Sea Devil The Sea Devils , once called the Aquatic Silurians ( PROSE : " Blood Heat " ) , were amphibious Earth reptile s . Like their land - based cousins , the Silurian s , they lived in prehistoric times in a scientifically - advanced civilisation . As their aquatic colonies awoke from suspended animation , these one - time rulers of the Earth attempted to reclaim their planet , leading to conflict with the new rulers : human kind . Biology . The Sea Devils were related to the Silurian s , though they were genetically divergent enough to create problems for the offspring of such matings . ( PROSE : " The Scales of Injustice " ) Like the Silurians , variations existed among the Sea Devils with different subspecies and appearances . Sea Devils typically looked somewhat like humanoid turtle s or plesiosaurs . They had beak - like mouths , large eyes , two fins on their head and long necks . They had three webbed digits on their hands and feet . Their skin tones came in a variety of shades , including green , blue and orange . They were much tougher than human s , since they needed to survive the crushing depths of the ocean . Sea Devils communicated in a language like sonar , but they could speak human languages in a whispering , rasping voice . ( TV : " The Sea Devils " ) A Sea Devil ' s skin was slimy to the touch . ( PROSE : " The Silurian Gift " ) One group of Sea Devil warriors , which appeared at Sea Base 4 , were notably distinguished by their silver skin and their lack of head fins . ( TV : " Warriors of the Deep " ) Another subspecies of Sea Devil , suggested by the Twelfth Doctor to be a " warrior - class " , were larger , faster , and stronger than those that he was familiar with . Their muscular bodies sported dark green skin , small red eyes , a pronounced jaw , and a large tail . They lived on Ravenscaur Island . They could communicate using a form of sound - based telepathy and could use this ability as a weapon by producing a deadly sonic scream . ( COMIC : " Clara Oswald and the School of Death " ) There also existed a class of Sea Devils who were much smaller , about the size of an infant human , that could merge with a human host , creating a human - Sea Devil hybrid but with the Sea Devil ' s psyche dominating its host . They possessed the sound - based abilities of their warrior - class counterparts but also displayed potent psionic powers , specifically telekinesis . The Twelfth Doctor explained that this was a side effect of two minds merging into one . Culture . The Sea Devils worshipped the Great Old One known as Dagon as their god . ( PROSE : " All - Consuming Fire " ) They were determined to retake the planet from the humans . They held an unwavering view that , as the original rulers , it would always be their right to do so . ( TV : " The Sea Devils " ) Technology . The Sea Devils were more advanced than the human s of the 20th century when they went into hibernation . They had colonies around the world , each filled with thousands of Sea Devils . ( TV : " The Sea Devils " ) The colonies could be awakened " en masse " through the use of a sonic signal . ( TV : " The Sea Devils " ) They built their underwater colonies inside caves . One base , located near a sea - fort , had simple grey - black - coloured walls , ( TV : " The Sea Devils " ) while another appeared to be carved into the rock , and was covered in algae and seaweed . ( TV : " Warriors of the Deep " ) They also used special orange capsules to transport land - dwelling creatures . ( TV : " The Sea Devils " ) The Sea Devils had stockpiles of weapons in these bases . They typically used small , round , side arms . ( TV : " The Sea Devils " ) During their invasion of Sea Base 4 , they made use of a larger version of the device to cut through the doors . ( TV : " Warriors of the Deep " ) The Sea Devils which attacked HMS Seaspite wore gauze - like dresses . ( TV : " The Sea Devils " ) The Sea Devils warriors in the 2084 invasion wore thick black armour reminiscent of samurai armour . ( TV : " Warriors of the Deep " ) The Sea Devils that attacked Ravenscaur Island had an enormous underground colony located in a network of caves that artificially reproduced the environment and climate of prehistoric Earth , indicating they had advanced terraforming and environmental technology . They had colossal war machines that were shaped like giant metal spheres with tentacles that could pierce through the hull of a human battleship easily . Sea Devils also had large submarines heavily armed with laser armaments that could easily outmatch an aircraft carrier with its speed and firepower . A fearsome piece of technology they possessed was sonic destructors . These were enormous tower - like structures that produced sonic pulses capable of sinking an entire island by causing intense earthquakes . History . Dominance . The Sea Devils ruled the Earth when human s were ape s , just as the Silurian s did . ( TV : " The Sea Devils " ) Both the Silurian and Sea Devil races were led by the Triad , their " custodians " . ( TV : " Warriors of the Deep " ) When the Moon approached Earth , ( TV : " Doctor Who and the Silurians " ) the Silurian and Sea Devil scientists calculated a great catastrophe in which " all life " would be wiped out ( TV : " Doctor Who and the Silurians " , " The Sea Devils " ) by the Moon " sweep [ ing ] by Earth " ( PROSE : " Doctor Who and the Cave - Monsters " ) and drawing away the atmosphere . ( TV : " Doctor Who and the Silurians " ) The Third Doctor repeated the claim to Marc Marshall that the Silurians built the shelters when they thought the planet would " suck away " Earth ' s atmosphere as it rushed by . ( PROSE : " The Scales of Injustice " ) Conversely , the Fifth Doctor recalled that the Silurian astronomers predicted that Earth was about to be " struck " by the planet at the time , ( PROSE : " Warriors of the Deep " ) and the Eleventh Doctor described the trajectory of the planet the astronomers had predicted as a " crash course " . ( TV : " Cold Blood " ) The catastrophe did not happen as predicted , and the Sea Devils remained inside their hibernation unit s . During millions of years of hibernation , the reactivation machinery of the hibernation units deteriorated . ( TV : " The Sea Devils " ) Awakenings . A lone Sea Devil scientist was prematurely awakened around the late 16th century due to a defective hibernator , proceeding to study how the world had changed during his sleep . After ten years , the Sea Devil rescued and befriended a human , Diego de Columba of Cordoba , who had washed up on the beach . Unfortunately , the Sea Devil was later captured by pirate s , one of whom inadvertently activated his device which called a creature to awake from under the sea , proceeding to destroy the pirates ' ship . Diego presumed the Sea Devil to have perished with the pirates . ( COMIC : " Devil of the Deep " ) In 1909 , a group of Sea Devil woke up beneath Raven Peninsula . They used terraforming technology to create an earthquake which separated the peninsula from the main land . Ravenscaur became known as Raven ' s Isle . The Sea Devils infiltrated the school and village on the island by turning the humans into Sea Devils . ( COMIC : " Clara Oswald and the School of Death " ) In 1972 or 1982 , ( COMIC : " Clara Oswald and the School of Death " ) a group of Sea Devils hibernating beneath the English Channel were awoken by . He attempted to persuade them to reclaim the planet from the human race . Despite the Third Doctor ' s efforts to convince them otherwise , hostilities escalated when Private Secretary Walker ordered the Royal Navy to attack the base , and the Sea Devils decided to go to war with the humans . However , before they could use the Master ' s sonar device to reactivate more bases , the Doctor blew up their base by overloading the devices by reversing the polarity , preventing the war between humans and Sea Devils from starting . ( TV : " The Sea Devils " ) In 1983 , Sarah Jane Smith and K9 , visiting Warren Martyn ' s archaeological expedition in Egypt , discovered an underground city of Silurians and Sea Devils . Sarah Jane opened diplomatic relations with them . On her return to England , she contacted the Brigadier , who wished to make amends for his earlier mistakes . ( COMIC : " City of Devils " ) In the early 21st century , a colony of both Silurians and Sea Devils were discovered under the South Pole . After a corrupt businessman attempted to blackmail them into providing him with a unique energy source , they revolted , with the Sea Devils launching an attack . They were forced back into hibernation by the Eleventh Doctor , who collapsed the crevice leading to their colony afterwards . ( PROSE : " The Silurian Gift " ) A colony of Sea Devils were awoken in 2084 by the Silurians . They were sent as shock troops to invade Sea Base 4 . Though they were better prepared , they were all killed by the Hexachromite gas used by the Fifth Doctor . ( TV : " Warriors of the Deep " ) Post - contact . By the 26th century , the inter - species conflicts appeared to have come to an end . Silurians and Sea Devils were accepted into Earth society , and the term " Earth Reptile " was apparently popularised among humans . ( PROSE : " Love and War " ) Around the 26th century , a number of Sea Devils and humans colonised the planet Chosan , which was being attacked by Calabraxian terrorists . The Earth Reptile Council asked the Braxiatel Collection for aid . They sent Bernice Summerfield . She found the ocean planet held a sentient protein in the waters which had began to infect the water - dwelling Sea Devils . The entities attempted to possess the Sea Devils and use them as an army against the humans but faced difficulty in integrating themselves into the host ' s biology . This led to mutations . They took the Sea Devil Lurnix as a host . They tried to have Lurnix lower the security grid and infect all the Sea Devils for an army . However , Bernice Summerfield evacuated the colony and detonated a bomb at Chosan , ending that threat . The Sea Devils were forced to abandon the Chosan colony due to the continuing threat . ( AUDIO : " The Poison Seas " ) In the 30th century , the Earth Reptiles were part of the Earth Empire and were considered full members of that government as an Earthborn species . ( PROSE : " So Vile a Sin " ) In the 32nd century , it became illegal to trade in Earth Reptile pituitary analogue extract on the planet Dramos . ( PROSE : " Burning Heart " ) In the 101st century , the Earth Reptiles were part of the Union . ( PROSE : " The Crystal Bucephalus " ) Undated events . During the Last Great Time War , a Sea Devil was imprisoned by an unknown force . ( COMIC : " The Forgotten " ) A group of Sea Devils were imprisoned in the TARDIS by the Master . ( GAME : " Destiny of the Doctors " ) A Sea Devil was worth an unidentified amount of points in the I - Spyder Book of Earth Creatures if it was spotted . ( PROSE : " The Last Dodo " ) As shown in the Anubian Book of Deliverance , the Anubian s attacked the Sea Devils . ( TV : " Curse of Anubis " ) A Sea Devil visited the beach on Beachelguese with a Silurian and a Macra . ( COMIC : " Surfshock " ) Alternate histories . In one alternative version of the 1990 s , the Doctor having died during the Wenley Moor incident , the Silurians ruled Earth unchecked while the Sea Devils served them as underwater soldiers . ( PROSE : " Blood Heat " ) In an alternate timeline created by the Black Guardian where the First Doctor never left Gallifrey and became Lord President , the Sea Devils and the Silurians fought over the Earth along with several species of alien invaders . This timeline was destroyed when the Seventh Doctor retrieved the Key to Time . ( COMIC : " Time & Time Again " ) In an alternate dimension in which the Doctor ' s adventures existed as a fictional TV show called " Doctor Who " , a fan dressed as a Sea Devil was present at a " Doctor Who " convention which the Eleventh Doctor visited with Ally in 2013 . ( COMIC : " The Girl Who Loved Doctor Who " ) The Sea Devils of Mondas . The planet Mondas had lifeforms identical to Sea Devils . ( COMIC : " The Hungry Sea " )