User blog comment:Chad from Accounting/what would happen if a fishmen ate a df they'd still be able to breath under water but could they still swim/@comment-1327586-20110307084643

it has happened, van der decken, in the current arc has eaten a devil fruit that allows hit to target anything he touches, no matter where he is. the result is that while he is able to breath and move (somewhat) he looses all ability to swim, and his power still works under-water