Sandal-type Boat Shoes
The Keens my wife bought me have been great (Men's Newport H2). They provide toe protection and are comfortable enough to wear all day. Grip has been pretty good under wet conditions probably better than my sneakers. The only drawback so far was when my heel slipped out after catching the back of the sandal on a lifeline while working with the mainsail. I've since tightened them up some.