The Triseraquins are ocean-dwelling creatures living on Earth.
The Triseraquins once lived on top of the seas until Aku sunk their city. Aku then told them if they wanted their city to be brought back up to the surface, they had to capture Jack. However, the Triseraquins realized that Aku tricked them and rescued Jack. They were seen in a cameo in Episode XLIII: The Aku Infection.
Fifty years later, they are among the known groups who witnessed Aku's triumphant broadcast. They retaliated immediately by storming The Pit of Hate with the Samurai's other allies and attacked Aku from the air using their Jelly-Whales. Some of them were defeated when Aku's forces (made from corrupted members of the Woolies and The Blind Archers' race) forced them off their airborne creatures using their enhanced jumping ability and claws. Some of them were killed by Aku's rain of spikes.
It is unknown how the past Aku's destruction affected their existence in the future.
Triseraquins are a highly-intelligent species, capable of building time machines, creating elaborate disguises and plots, and building cities underwater that can sustain non-aquatic life.
They are amphibious, meaning they are capable of surviving on land or in water, though they require water helmets to survive for prolonged amounts of time without moisture. They have a set of gills along their long necks and three, antenna-like protrusions on their heads. They are also incredibly tall (perhaps twice as tall as Jack) and have large hands with bulbous fingertips. They all have UK accents; Ringo speaks with an accent similar to Ringo Star, Guiness' accent is similar to Alec Guinness', and Connery's is similar to Sean Connery's.