Hi, I've been diving now 6years while detecting,I use a Sea Hunter and whites Beach Hunter 300,I also own one off them,I found the 740 not much good,to small to detec under water,it only detects maybe 2inchs at best,I found it best around rocks,you are talking about a dive belt may I say make sure you practise under water taking that off, you can get in trouble very quick if things go wrong believe me I've seen it.If you want to go underwater detecting do a dive course,there is a lot to learn about underwater detecting.I have found great things underwater sometimes up to 8meters deep you carnet don't that with. Dive belt.Good Luck.