Yes, Namor described him thusly: "A worse swimmer you have never seen." Wolverine agreed: "Namor's right, I can't swim for shit."
I actually read a theory on someone's blog somewhere that Wolverine's skeleton is so dense and heavy (like a few hundred pounds) that just moving causes enormous muscle strain, but his regenerating factor heals the damage as soon as it's done, so aside from some pain, it doesn't matter much. That would explain why in The Wolverine movie, when he starts losing his healing factor, he slows down a lot.