I have owned the near identical Etrex Venture Cx for over 3yrs now. Same size, button layout and colour screen as the Vista HCX.
I have marine mapping for the areas I visit and it has been a huge addition to safety and convenience when out on the several small boats and sibs we've owned over that time.
Decent battery life with easily available AAs, waterproof aspect tested and passed (!), functions perfectly easy to operate on the move, absolutely no complaints.
Obviously for higher speeds on a large RIB a fixed unit with decent screen size is more appropriate but having this unit totally self contained in your pocket is ideal on smaller craft.