I'll be starting an Apocalypse World (hopefully 2nd ed) in later August.  We're planning on using Waterworld as inspiration for the setting; land is very rare, water everywhere.  Getting place to place by boat, possibly swimming.  Not sure if "Smokers" will show up or not. 

I kind of want offer a special "move" allowed only during character creation that would allow a character to have gills and webbed hands and feet for better swimming.  It wouldn't necessarily allow them to do extra deep (like below 60 meters), but would allow for actions that otherwise wouldn't be as feasible. 
I'm not sure how to handle this with Apocalypse World.  I feel like it should be a special move, but admittedly, this will only be my second time working with the system.