boat shoe

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A moccasinlike canvas or leather shoe having a rubber sole designed to provide traction on wet surfaces.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A type of casual footwear resembling a loafer, originally designed to be worn aboard a boat, characterized by water-resistant hide, soles designed to improve hold on wet deck of the boat and side lacing.