Be careful, when they say waterproof, they're talking about the search coil only.
I know you already bought it, but in general, Whites and Garretts tend to be the best reviewed.
Metal detectors use one of three technologies:
•Very low frequency (VLF)
•Pulse induction (PI)
•Beat-frequency oscillation (BFO)
Most Bounty Hunters are BFO types if I remember correctly. They work, but depth is limited.
I bought a White XLT Spectrum about 10+ years ago. Ran me about $850 back then though.
I use it for searching old, long forgotten, local historical sites. I've collected original 18th & early 19th century local history books and maps/atlases that I use to research for places to hunt.
Being in the midwest, beach huinting is only during vacations for me. Local lakes with a swim area can be good spot as well since people tend to lose a lot of stuff there.
Parks and playgrounds are usually good for a few coins.
Be advised, once you find something, the treasure hunting bug bites hard !
Happy detecting.
BTW:
Bring plenty of extra batteries when you go.