Some characters i designed to occupy the sea-tunnels in my comic book. Its a pretty nasty place to live, but you can get big if you try hard enough. Theres allot of blues and greens in the tunnels, all of the windows are underwater, of course, so all the natural light is tinted a bit deeper blue than usual. Gang members down here tend to wear brighter colors or florescent bands to identify themselves. (you can see the big guy with an aqua band around his arm)
There isnt much money to be made in the tunnels other than as a transport-worker. These guys sort of function like railway workers. they direct the huge loads of cargo around the tunnels. There are directors (like the weird, old cat) who practically never leave their vehicles, and theres the Guards who... well... guard the cargo. (see the bear)
and then, of course, theres scroungers: tiny ppl who pick through the muck and mildew to collect bits of fallen cargo and whatever winds up stuck down there. There are various drainage, pressure, and forgotten pipe-systems that the little-ones live in. theres never a shortage of places to hide when you`re small enough to sell loose buttons. (the lizard-girl up top is supposed to be tiny, carrying a fishhook)