Use 'waterproof' to describe items that protect against rain or water. She bought a waterproof camera for her beach vacation.
Pro Tip 2/3
Not Submersible
'Waterproof' implies protection from surface water, but often not when fully submerged. His watch is waterproof, but he shouldn't go diving with it.
Pro Tip 3/3
Misleading Context
Sometimes products are labeled 'waterproof' for marketing, so check their actual capabilities. This 'waterproof' phone case failed when I swam with it.