Don't pocket water while underwater

This should fix issue #7797
Why do you create a copy of the perfectly good water item (the parameter of that function) here? Btw. This will magically transform salt water (from `iexamine::swater_source`) to normal water. If you need this copy, why not use the copy constructor: `item water_temp(water);`, it will copy *all* relevant properties of the item? Most likely you don't need the copy at all, because `inventory::push_back` creates its own copy anyway.