i am such a fucking nerd that i sit and think about this.
so i don't have a good reference pic of him on hand, you'll have to use your imaginations
viral's generally considered to be part shark, feline, and ape (human or otherwise)
the obvious characteristics are cat eyes, shark teeth and bizarro cat monster gorilla hands, but i like to try and further incorporate animal characteristics into him
shark: the teeth, obviously, and like a shark he can probably lose and replace them easily. it would make sense if he had a lot more bite force than a human, too. it's subtle, but his mouth is always drawn very differently from the humans' in the series - not just the teeth, it's far too wide, which seems to imply he has no or reduced cheeks. i don't know enough to go into the relationship between cheeks and jaw muscles and brain size / skull structure (but they all relate to bite behavior and force) humans have sacrificed almost all of their senses and bite force to have a big fat giant brain so genome must have somehow gotten around the problem of giving viral fat jaw muscles that somehow don't crush his brain when he bites down.
in crush i give him gills at his throat. for whatever reason, a lot of times when humanoids are given gills in fiction they're placed around the chest -- i guess it's because that's where the lungs are, but in every form they appear in in nature puts them at the throat. my ichthyology is really goddamn rusty (okay it was never there to begin with but) so i don't know a whole lot of technical details about how gills work without looking at wikipedia or something, but basically they're in the throat so water passes over them when the fish 'inhales' and takes in water through his mouth. in some pictures you can almost see down a fish's gullet and see slits of light where the gills are.
cartilaginous skeletons. it would be interesting if he had one, it would certainly make it easier for him to take adiane's abuse. i'm not sure how well they translate to terrestrial use though.
faptian intermission
rescue missionsense of smell. both species could give him a fantastic sense of smell (who knows where he's keeping the scent receptors since he barely has any kind of nose but)
vision. probably fairly humanlike (the one sense we can be proud of) with better night vision given the feline nature of his pupils (though sharks also have eyes like that and since they came first shouldn't we say felines have shark-like eyes????) also, nictitating membranes (second eyelids) are something both cats and sharks have, so it would be strange if he didn't have them too - i can see him using them when he swims to modify his vision for underwater use.
claws. his claws are cool but goddammit they make porn hard. i know i had them be retractable in one lemon but that's really completely implausible (lol) - claws that are retractable have a very distinct, spring-loaded finger design, basically taking what we would recognize as a finger and bending and packing it back into the paw.
his hands and arms have always been kind of interesting to me. the weird popeye structure is strange but the length and lankiness of his arms makes them look far more great ape than human, which would imply that likewise he's far stronger than a human (though this sort of clashes with his shark side since apes' thick bones and big muscles make them too heavy to swim. that humans can swim and take so well to water is *weird*.)
what else, uh. episode 3 shows that he has pretty extreme reflexes and speed when he wants to, though this is about the only time you see them.
this prison episode also revealed that he's a skinny motherfucker, indicating he has a high metabolism, which would make sense given all of the above resources his body is fueling (not to mention the healing system genome put in place). so he probably needs to eat a lot all the time. which is weird since we never see him eat once. hmmmmmmmmmmmmm.
finally, the most important part i have
already covered though let us all hope for yoko's sake i am wrong.