Underwater Encounters (OSS)

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Because of the incredible diversity of aquatic life, it is likely that underwater adventurers will eventually stumble into a marine encounter. The encounter tables detailed below allow the DM to tailor random encounters to the specific area in which the heroes adventure. These tables can easily be modified to fit individual campaign worlds. After all, a world where merrow are common would have a greater frequency of merrow encounters.
==Dungeon Mastery Tip: Encounters==
Although random encounters only occur a set number of times per day (most tables require a check about three times in a single day), the undersea world brims with life. The Dungeon Master should paint a vivid backdrop for the players. Little details go a long way towards setting a mood and conveying the feel of underwater life.
When running an adventure that occurs in shallower depths (600 feet or less), the density of undersea life should keep players on their toes: undersea plant life undulates to rhythmic currents, many bottom feeders crawl, burrow, and slither across ocean floors, and schools of fish dart about the depths, chased by the occasional predator.
At greater depths, the undersea world is a dark, mysterious realm-a place of danger and terror. Many of the sea giants (such as giant squid, clams, whales, and so on) make their homes in these depths. The players should begin to feel unsettled as they travel within this brooding, hostile, environment.
DMs should also note that not every encounter must end in combat. In fact, the poor visibility and alien nature of the undersea world makes a shadowy, insubstantial figure lurking at the edge of a character's vision that much more frightening. And even the mere presence of a shark or other predator within the same area is enough to unsettle players.
==Encounter Distance==
In open water, visual range governs encounter distance. Encounters usually take place at about Type range (see Tables 39-41). Characters can detect movement at a greater range, but parties who become alarmed at every little movement are going to spend all their time jumping at shadows and precious little time adventuring.
If the local environment offers some cover, use Table 58 from the DUNGEON MASTER® Guide to determine encounter range unless the prevailing visibility dictates a shorter distance.
==Continental Shelf==
Check for random encounters three times a day. Encounters occur on a roll of 1 or 2 on 1d6. (The saltwater encounter tables from the MONSTROUS COMPENDIUM® Annual, Volume Two are quite suitable for continental shelf encounters. DMs seeking a greater variety might wish to use those if the die roll result was a 1 and the table provided below if the roll was a 2.)
 Table 49: Continental Shelf Encounters (d12, d8)
2 	Ray, ixitxachitl/Lamprey, giant
3 	Kelpie
4 	Aquatic Jelly
5 	Urchin, red
6 	Shark (5-6 HD)
7 	Sea Lion
8 	Dolphin/Narwhal
9 	Whale, killer
10	Fish school or special
11	Aquatic race (roll on Table 57)
12	Whale, common
13	Man o' War/Jellyfish
14	Urchin, black
15	Shark (3-4 HD)
16	Hippocampus/Kapoacinth
17	Seahorse, giant
18	Shipwreck or special
19	Eel, marine
20	Urchin, yellow
==Continental Slope and Rise==
Roll 1d6 three times each day. Random encounters occur on a roll of 1 on 1d6.
 Table 50: Continental Slope and Rise Encounters (d12, d8)
2 	Ray, ixitxachitl/Lamprey, giant
3 	Dragon Turtle
4 	Whale, giant
5 	Aquatic Jelly
6 	Squid, giant
7 	Jellyfish
8 	Dolphin/Narwhal
9 	Fish School or special
10	Whale, common
11	Aquatic race (roll on Table 57)
12	Whale, killer
13	Seaweed or special
14	Shark (3-5 HD)
15	Shark (5-6 HD)
16	Shark (7-8 HD)
17	Hazard (see page 125)
18	Shipwreck or special
19	Shark, giant
20	Morkoth
==Abyssal Hills and Plains==
Check for random encounters twice a day. An encounter occurs on a roll of 1 on 1d6.
 Table 51: Abyssal Hills and Plains Encounters (d12, d8)
2 	Eye of the Deep
3 	Dragon Turtle
4 	Snake, giant sea
5 	Shark, giant/Whale, giant
6 	Shark (7-8 HD)
7 	Shark (5-6 HD)
8 	Whale, killer
9 	Octopus
10	Eel, marine
11	Aquatic race (roll on Table 57)
12	Hippocampus/Kapoacinth
13	Fish school or special
14	Eel, giant
15	Eel, electric/Lacedon
16	Dragonfish
17	17 Hazard (see page 125
18	Giant
19	Squid, giant
20	Morkoth
==Oceanic Trench==
Because these areas are home to rather large and dangerous creatures, the trench encounter table contains only a few possible encounters. DMs should use this table cautiously, as one random encounter could decimate an entire party.
Characters adventuring in an underwater trench have a 15% chance per day of a random encounter. DMs should roll a 1d8 and consult the following list to determine the nature of the encounter:
 Table 52: Oceanic Trench Encounters (d8)
1	Kraken
2	Dragon Turtle
3	Snake, giant sea
4	Squid, giant
5	Octopus
6	Eye of the Deep
7	Worm, mottled
8	Morkoth
==Seamounts and Guyouts==
Roll twice a day for random encounters. Encounters occur on a roll of 1 on 1d6.
 Table 53: Seamount and Guyout Encounters (d12, d8)
2 	Jelly, aquatic
3 	Shark, giant
4 	Whale, giant
5 	Ray, manta/Octopus
6 	Shark (7-8 HD)
7 	Ray, sting
8 	Dolphin/Narwhal
9 	Eel, weed
10	Fish school or special
11	Aquatic race (roll on Table 57)
12	Whale, common
13	Jellyfish
14	Eel, electric/Lacedon
15	Seahorse, giant
16	Eye of the Deep
17	Hazard (see page 125)
18	Hippocampus
19	Dragonfish
20	Octopus, giant
==Oceanic Ridge==
Check for random encounters three times a day. Encounters occur on a roll of 1 on 1d6.
 Table 54: Oceanic Ridge Encounters (d12, d8)
2 	Shark, giant
3 	Octopus, giant
4 	Snake, giant sea
5 	Dragonfish
6 	Octopus
7 	Whale, common
8 	Shark (5-6 HD)
9 	Kelp forest or special
10	Eel, weed
11	Dolphin/Narwhal
12	Fish school
13	Aquatic race (roll on Table 57)
14	Jellyfish
15	Eel, marine
16	Whale, killer
17	Hazard (see page 125)
18	Shark (7-8 HD)
19	Giant
20	Ray, ixitxachitl/Lamprey, giant
==Coral Reef==
Check for random encounters three times a day. Encounters occur on a roll of 1 on 1d6.
 Table 55: Coral Reef Encounters (d12, d8)
2 	Shark, giant
3 	Ray, ixitxachitl
4 	Giant
5 	Shark (7-8 HD)
6 	Urchin, red
7 	Sunken ship or special
8 	Shark (5-6 HD)
9 	Fish school
10	Eel, weed
11	Shark (3-4 HD)
12	Aquatic race (roll on Table 57)
13	Urchin, green
14	Ray, sting
15	Crab, giant
16	Lobster, giant (crayfish)
17	Hazard (see page 125)
18	Eel, marine
19	Worm, mottled
20	Urchin, silver/Urchin, yellow
==Rivers and Lakes==
Roll for random encounters twice a day. Encounters occur on a roll of 1 on 1d6. (The DM may wish to use the freshwater encounter tables from MONSTROUS COMPENDIUM® Annual, Volume Two instead of the one given here.)
 Table 56: River and Lake Encounters
2 	Dragon Turtle
3 	Nymph
4 	Otter
5 	Catfish/Leech, giant
6 	Kapoacinth/Lamprey
7 	Lizard man
8 	Koalinth
9 	Beetle, giant water
10	Spider, giant water
11	Fish school or special
12	Pike, giant
13	Crayfish, giant
14	Pirhana/Quipper
15	Nixie
16	Gar, giant
17	Hazard (see page 125)
18	Lacedon
19	Naga, water/Eel, giant
20	Vodyanoi
 Table 57: Aquatic Races (1d8)
1	Merrow
2	Elf, sea/Selkie
3	Locathah/Scrag
4	Merman/Seawolf, lesser
5	Sahuagin/Seawolf, greater
6	Sirine
7	Triton
8	Tako/Marid
==Encounter Descriptions==
Several encounter types need further description, as noted below. In cases where an encounter lists two creatures separated by a slash, the actual creature encountered will depend on the climate or a die roll; also see notes below:
Catfish/Leech, giant: There is an equal chance to encounter each type of creature.
Dolphin/Narwhal: Dolphins often follow submerged adventurers about, playing with them and possibly assisting if the party gets into trouble.
Dolphins shun very cold (arctic or subarctic) waters. In these areas roll 1d6. On a roll of 1-4, no encounter occurs. On a roll of 4-6, a narwhal appears instead of dolphins.
Eel, electric/Lacedon: Electric eels remain active around the clock, but lacedons are mostly nocturnal. During daylight hours, roll 1d6, on a roll of 1-5 the encounter is with an electric eel. On a roll of 6 a lacedon appears instead. At night, there is an equal chance to encounter either type of creature.
Elf, sea/Selkie: Sea elves are found only in temperate, subtropical, and tropical waters. Selkies are found only in colder waters.
Giant: The encounter might be with a storm giant, reef giant, or titan at the DM's option. Reef giants dwell only in warm waters. Storm giants and titans generally live only in warm or temperate waters, but might visit cooler seas to hunt or gather treasure.
Hippocampus/Kapoacinth: There is an equal chance for either type of creature to appear.
Kapoacinth/Lamprey: Lampreys are saltwater creatures that occasionally migrate to fresh waters via deep, slow rivers or canals. Lampreys do not appear in landlocked lakes. Otherwise, there is an equal chance to encounter either creature.
Locathah/Scrag: In tropical or subtropical waters, roll 1d6; on a roll of 1-3 the encounter is with locathah, on a roll of 4-6 scrags appear instead. Locathah are not found in cooler waters.
Merman/Seawolf, lesser: In temperate waters, roll 1d6; on a roll of 1-3 the encounter is with mermen, on a roll of 4-6 lesser seawolves appear instead. Mermen are not found in cold waters and seawolves are not found in warm waters.
Man of War/Jellyfish: A man o' war poses a danger only to creatures swimming within 30 feet of the surface. At the surface, there is an equal chance for encountering either creature; farther down only jellyfish will appear.
Naga, water/Eel, giant: Naga dwell only in tropical or subtropical waters. Giant eels can be found in temperate and subarctic waters. In arctic waters, no encounter occurs.
Piranha/Quipper: Pirhana dwell only in tropical or subtropical waters; quippers dwell in temperate waters. In subarctic or arctic waters, no encounter occurs.
Ray, ixitxachitl/Lamprey, giant: Ixitxachitl are found only in warm waters and usually only at fairly shallow depths (though they might dwell near thermal vents). If the water is too cold or deep for ixitxachitl, a giant lamprey appears instead.
Sahuagin/Seawolf, greater: In temperate waters, roll 1d6; on a roll of 1-3 the encounter is with sahuagin, on a roll of 4-6 greater seawolves appear instead. Sahuagin are not found in cold waters and seawolves are not found in warm waters.
Shark, giant/Whale, giant: These creatures plumb the depths looking for prey. Giant whales ignore adventurers unless disturbed, but giant sharks tend to attack. There is an equal chance to encounter either type of creature.
Tako/Marid: In tropical or subtropical waters, there is an equal chance to encounter either type of creature. Tako are not found in cooler waters. Marids generally do not dwell in very cold waters, but may visit them to hunt or seek treasure.
Urchin, silver/Urchin, yellow: There is an equal chance to encounter either type of creature.
===Special Encounters===
Dungeon Masters can use special encounters to add mystery and flavor to underwater adventures. In addition, these special encounters provide an alternative to combat-oriented random encounters. DMS should feel free to use any of these encounters as "mood setters" during the course of an adventure.
Fish School: Fish schools are large groupings of particular fish species-much like herds-that swim about in the ocean. These schools mill about and obstruct vision. Characters caught within a school of fish cannot see more than 5 feet regardless of water clarity. In addition, schools containing small-sized and larger fish inflict 1-2 points of buffeting damage per round to those creatures caught within their area. Schools usually mill about in a general area for 1d6 rounds.
Giant Clam/Pearl Beds: Occasionally, giant clams will congregate around a certain area, such as a hydrothermal vent. There is a 10% chance that an individual clam contains a pearl worth 1,000-10,000 (10d10x1,000) gp. Giant clams snap shut in response to the slightest disturbance.
Clam, giant: AC 0; MV 0; HD 10; THAC0 11; #AT 1; Dmg 1d12; SA Entrapment; SZ M (6' diameter); ML fearless (20); Int Non (0); AL N; XP 1,400.
Notes: SA-A successful attack roll causes 1d12 points of damage and traps part of the damaged creature inside the clam. Wrenching a trapped character free of a clam requires either slaying the clam or making a successful bend bars attempt.
Kelp Forest/Seaweed: This is an area of the ocean bottom heavily covered with thick green seaweed or kelp in floating masses or beds. In many cases, this underwater vegetation spans a great distance thus deserving the title "forest." Movement within seaweed- covered areas occurs at half the normal underwater swimming or walking rate (rounded down) unless assisted by magical means (such as a free action spell). In addition, seaweed or other thick underwater vegetation severely restricts visibility. The Dungeon Master should consider the water clarity within these areas as murky for purposes of underwater vision.
Sunken Ship: Occasionally, ships do not survive the harsh elements of the sea. These sunken ships now rest on the bottom of the ocean. If a party explores the wreckage, the ship is occupied on a roll of 1 or 2 on 1d6. The DM should assign a resident or roll on the encounter table for the surrounding underwater geography.
Sunken ships make great side-treks or even separate adventures. DMs should not overuse this special encounter, as their players may lose interest in exploring "yet another" sunken vessel.
===Underwater Hazards===
The following table lists a number of possible underwater hazards. Used correctly, these hazards can enhance a player's experience of the dangers inherent in undersea exploration. If the underwater encounter tables given above indicate the presence of a hazard, the fah Dungeon Master should simply choose the one most appropriate to the characters' current location and the storyline's demands (although hazards can be determined by a die roll). For example, heroes adventuring in an arctic area will certainly never encounter poisonous coral, unless the coral is magical and the encounter adds to the overall narrative of the adventure.
 Table 58: Underwater Hazards
1 	Sea Tremor
2 	Shark Feeding Frenzy
3 	Predatory Fish Attack
4 	Poisonous Coral
5 	Whirlpool
6 	Swirling Current
7 	Elemental Vortex
8 	Sandslide
9 	Hydrothermal Vent
10	Jellyfish School
Elemental Vortex: This hazard resembles a small but powerful whirlpool and only appears at the bottom of a deep ocean trench. Such magical phenomena are extremely dangerous, as any creature moving within 15 feet of a vortex must make a successful saving throw vs. breath weapon at a -4 penalty or be pulled into the Plane of Elemental Water. Characters entering the plane without water breathing magic will quickly die.
Vortices are extremely rare and deadly; Dungeon Masters should use them with care in their campaigns. However, DMs interested in the PLANESCAPE® setting can easily use an elemental vortex as a springboard to the planes.
There is a 5% chance per hour that a creature from the Elemental Plane of Water will appear through the vortex. If such a creature is indicated, roll 1d8 and consult the following table to determine its type:
 Table 59: Elemental Dortex Encounters (1d6)
1	Elemental Vermin, Spitter(MONSTROUS COMPENDIUM® Annual, Volume I)
2	Nereid
3	Mephit, Ice
4	Mephit, Water(PLANESCAPE® MONSTROUS COMPENDIUM® Annual I)
5	Water Elemental
6	Water Weird
Hydrothermal Vent: Characters swimming or walking directly above a hydrothermal vent suffer 1d6 points of damage from the heat and pressure. In addition, the force of the superheated water pushes the character up 6d10 (60 to 100) feet. A typical vent produces a hazardous area (capable of inflicting heat damage) 5 feet in diameter and 20 feet high. Certain intelligent creatures use these vents to add speed and distance to an attack. Any creature utilizing this strategy receives a +1 bonus to its attack and damage rolls. The underwater "updraft" from a typical vent is 30 feet in diameter and 100 feet high.
Jellyfish School: A jellyfish school is a wide swath of floating jellyfish nearly 60 feet long and 15 feet deep. Characters unfamiliar with marine life will not recognize the dangers such creatures represent; they will see only a large group of floating "clouds" with filmy tendrils. Occasionally, fish dart in and out of the floating mass of creatures. (Of course, these are fish that are immune to the stinging nematocysts of the jellyfish.)
Any character near the area of the jellyfish school must make a saving throw vs. paralyzation to avoid being struck by the long, stinging tentacles of these creatures. Failure indicates that a character receives 4d6 stings, each inflicting one point of damage. Characters blundering into the school itself receive 10d10 stings from the jellyfish. Such unfortunate characters also must attempt saving throws vs. poison with a -4 penalty. Failure indicates that the character in question succumbs to shock from the amount of poison entering his body. Shocked characters stop breathing and fall unconscious. Unconscious characters immediately begin to sink or rise according to their encumbrance ratings (see page 76). Furthermore, characters who stop breathing can only survive for a limited amount of time (see Holding Your Breath in Chapter 14 of the Player's Handbook). A neutralize poison restores breathing and consciousness to a shocked character, but does not heal any damage caused by the stinging nematocysts.
Predatory Fish Attack: This hazard is more appropriate to lake and river adventuring. However, DMs can easily adapt it for use in an ocean environment. In any event, the characters encounter a school of (hungry) predatory fish which attempt to feed on them. The two most common sorts of predatory schools are barracuda (2d6) or piranha (5d10). These deadly fish randomly attack player characters until either they, or their prey, are killed. There is no chance that they will attack each other.
Poisonous Coral: The stunning, multi-colored beauty of the plants and animals within a coral reef often belies a dangerous nature. Some types of corals produce powerful defensive chemicals. Any character touching this type of coral suffers 1d2 points of damage and must make a successful saving throw vs. poison. Failure indicates that the victim suffers an additional 1d4 points of damage. Normal clothing offers no protection against contact, but armor does.
Sea creatures native to an area containing poisonous coral often prove immune to its effects, and unwary adventurers may suffer an unpleasant surprise when attacking or pursuing such creatures.
Sandslide: Sandslides occur when large amounts of sea sediment shift. The results of such a shift are roughly equivalent to an avalanche or landslide on the surface. Sandslides are particularly dangerous to creatures traversing ocean canyons and ridges. Characters caught within 20 yards of a sandslide need to make successful saving throws vs. paralyzation to avoid being buried underneath 10+5d6 feet of sand, mud, and other sediment. Furthermore, those struck by such underwater debris travel 5d10 feet away from the initial area in the direction of the falling sand. If the sandslide occurs on a steep slope or cliff face, the falling sediment pushes characters off of the area, causing them to sink at a rate of 80 feet a round until they reach the bottom. Proficient swimmers who spend more than one round sinking in this manner can attempt a single Strength check at a -6 penalty to escape the falling debris. Characters failing the check sink to the bottom and become buried.
Buried characters (even those who can breathe water) must hold their breaths until rescued (see Chapter 14 of the Player's Handbook).
Although the effects of water saturation on mud and other sediment make it impossible for other characters to free trapped creatures without the help of magic (such as dig spells), anyone buried in a sandslide can attempt a Strength check with a -6 penalty. Success indicates that the character in question begins to pull himself free of the sand at a per round rate of 5 feet plus two feet for each point of hit probability adjustment due to Strength. For example, a character with a Strength score of 17 (+1 hit probability adjustment) would move 7 feet (5 base +2 for Strength adjustment) every round. DMs should note that such movement counts as strenuous activity and limits the amount of time a character can hold his breath. If the initial Strength check fails, the character cannot free himself.
Sandslides worsen the water clarity of the surrounding area. Consider all water within a quarter mile from the sandslide as murky (see Table 41). After 1d6 hours, the water clarity within the affected area returns to normal.
Sea Tremor: Sea tremors are minor underwater quakes that occur as a result of plate tectonics or underwater volcanic activity. These tremors last anywhere from 2 to 5 minutes (1d4+1 rounds). Though not particularly deadly, sea tremors cause quite a stir. Thus, the chance for a random underwater encounter doubles for one full day after a sea tremor.
Sea tremors might trigger sandslides (see above) or cause underwater caves to collapse.
Shark Feeding Frenzy: Occasionally, the smell and taste of blood in the water whips sharks into a feeding frenzy, causing them to attack mindlessly any prey that presents itself-including each other. Usually, 3d4 sharks of various Hit Dice (between 3 and 8) participate in a frenzy. These creatures randomly attack any PC they sense. Assign each PC a number and roll dice appropriate to the number of characters. For example, the DM would roll 1d8 if the party contained 8 characters. The number rolled indicates which PC receives an attack from a shark. There is a 20% chance, however, that one or more frenzied sharks attack each other (determine the number randomly as noted above). DMs should check this percentage before randomly determining which PCs receive attacks. Frenzied sharks receive a +3 attack bonus and continue attacking until they, or their prey, are killed.
Swirling Current: Swirling currents reduce overall underwater movement rates by one third. Thus, a surface dweller whose total underwater movement rate is 6 would swim at an overall rate of 4 for the duration of the currents. Swirling currents last for 2d8 rounds before dispersing.
Whirlpool: These hazards frequently result from tidal forces in the ocean, and can appear quite suddenly. Tidal whirlpools usually last only a few hours, but appear in the same location twice a day. The tremendous pull exerted by these vortices causes Swirling Currents (see above) to appear within a half mile of the phenomenon. All characters within a quarter mile of a whirlpool must make successful saving throws vs. breath weapon to avoid being drawn into the vortex. Failure indicates that the creature in question moves toward the whirlpool at an underwater movement rate of 12. Pulled characters can make further saving throws vs. breath weapon each round to escape. Each round characters remain trapped in the pull, however, they suffer a cumulative -1 saving throw penalty (to a maximum penalty of -8). PCs who make successful saving throws can assist others in resisting the effect of the whirlpool. Characters receiving assistance gain a +1 bonus to their saving throw rolls for every character who helps them resist.
Once within the vortex of the whirlpool, characters swirl about for two rounds, suffering 2d6 points of damage each round. (During this time, they can continue to attempt escape as noted above.) After two rounds in the vortex, however, characters are dragged to the bottom and held there. Once so trapped, characters suffer 4d6 points of damage each round and cannot escape without assistance. Characters receiving assistance, as well as their helpers, must make saving throws vs. breath weapon with a -8 penalty to break free. A rescuer failing the saving throw becomes trapped too.