Cloak of Dryness (3.5e Equipment)
From D&D Wiki
The Cloak of Dryness is a plain black, hooded cloak made from smooth, black or yellow material. The cloak is especially cumbersome and hot to wear (although it will not protect one from the cold for some reason). While it only weighs thee pounds, it takes up seven pounds worth of encumbrance.
The wearer of a Cloak of Dryness need never fear getting wet. Even if completely submerged, the wearer will remain dry. This does not confer any ability to breathe water or survive underwater, nor does it assist with their ability to swim, they just won't need a towel afterward.