Underwater

To enter its depths unaided by human ingenuity is either the briefest of pilgrimages or a certain death sentence. To swim its alien waters is to voluntarily plummet many links down the food chain. 
:: --- Jarod K. Anderson, The Cryptonaturalist, Episode 2: Teacup Whale.
== Breathing ==
* Some creatures have gills, some can hold their breath for remarkable amounts of time
*SCUBA gear is a must, for air-breathers.
=== Settings ===
*Low tech adventurers, such as Armada-timeline salvaging teams, will likely be using diving bells and simple breath-holding to extend their range
*Those hired by the Duncorne Foundation to search the ocean floor are likely to use TL5 hard-hat diving suits
*Lightweight modern divers will often use SCUBA systems--or rebreathers, if they need to avoid bubbles for stealth missions, such as infiltrating the Lair of the Fat Man.
**Supposedly, metal "shark mail" helps with shark attacks, but not how you would think. It provides low DR, but prevents damage from small sharks and reefs (preventing bleeding), disrupts the EM field from the body, and makes the wearer smell like metal--which all make the wearer much less likely to be seen as "food" by a shark!
*Seekers of TL9 and beyond can push the envelope of amphibious travel with monster-resistant aquatic battlesuits. Perhaps a deep-sea research site needs some artifact samples picked up, but the samples are a few hundred pounds? You may need a marine combat walker for that!
**Rigid battlesuits are tough enough to resist bites from even the largest non-extinct sharks.
== Movement ==
Non-aquatic and non-amphibious creatures must make do with a swim speed. A personal propulsion system (gripped in the hands) or underwater jetpack can certainly help. Or perhaps 
== Communication ==
=== Effective ===
*Speak Underwater and Sonar! Some creatures like dolphins (regular and the punny kind) already communicate underwater using a variation of sonar. Any sapient aquatic race is assumed to have mastered speech underwater.
*Direct line, such as cables, or cable-towing drones
*Using simple Morse code through flashes of light
*Hand signals
=== Ineffective ===
* Regular air-based speech is garbled at best
* Aquatic speakers might work
* Radio has extremely limited range due to its diffusion in water
== Weaponry ==
See also: Shooting weapons underwater
=== Effective ===
*Bites and serpentine grapples
*Anything with a small cross-section, like a spear
*Concussive explosions are actually more powerful in water than in air
*Aquatic missiles, torpedoes, self-propelled weapons
=== Ineffective ===
* Swinging weapons are severely hampered
*Conventional firearms are at a major disadvantage. Some specialized "amphibious dart" bullets are less effected by water, but are still limited.
* Gauss and gravity rail weapons might hit harder, but still be hindered
* Most lasers
** Infrared lasers simply boil water
** Most lasers have limited range
** Blue-green lasers are the most effective in water, limited to about 60-150 yards.
== See Also ==
* A whole issue about Underwater Adventures
*Transhuman Space: Under Pressure has some hard sci-fi examples of humans and AIs living underwater
*Getting underwater often involves a lot of Swimming
*Perhaps someone can add a page about Pressure and Pressure Support!
**Resurface slowly to avoid getting the Bends
== Quotes ==
http://www.sjgames.com/gurps/faq/FAQ4-3.html#SS3.1.6 discusses penalties.
Category:Rules