All oceanic species live much longer life spans, in addition, the posses a genetic memory that gets passed from one generation to the next.
The genetically enhanced Craihs, Raiey and Neefla can sleep either normally or in the water. The first two have an easier time at it since they can breathe without moving. Neefla, still need air and the only purpose for sleeping in water would be for their skin. Not necessary, but it's more comfortable for them. Might take into account that they're also a good deal heavier than your average Cyantian or human of similar height. Neefla tend to be pudgy.
All three of these species are aquatic and do need periodic immersion to keep their skin from drying out.
Aquatics like tattooing and have many kinds of them. They especially like brightly colored and color-shifting ones, usually all stylized.
Reason why male Craihs and other Cyantian water dwellers do not have as pronounced gills: Males and females have slightly different ways of processing oxygen for stamina and thus filter the water at a different rate. Males would actually have broader flatter gills for filtering more water at a time, plus, their ribcages are broader, which spreads them out. Females have gills that are narrower because their diaphragms are higher as is their ribcage. It is rounder than broad. It makes them quite a bit faster than the males, although not as powerful. They can hold their own quite easily though.
The females build is also directly in relation to the fact that if she had a broad chest and were pregnant, she'd have a harder time swimming smoothly. This way, she's streamlined even when filled out with eggs (or at least, their ancestors were).
Aquatic seasons are tied to the temperature of the water, with going into season and the release of pheromones only occurring when conditions are right. It has been noted that whatever pheromones the aquatics emit travel only in the water. If they met out of the water, the males might be puzzled or disturbed by the sudden change in behavior; in the water, they would have reactions of their own. Also, Craihs and Raiey are closely related - the males of one species might even react to the pheromones of the other. Centuries ago, that might have just meant an easy meal...