I'm a relative newbie too, started with an ACE 250 that I bought about two years ago. It works great on land and in dry sand. It does not like wet sand -- meaning it just beeps non-stop when over the wet sand. Saltwater wet that is, I've never tried it near freshwater.
Like you, I live near the beach, and after only a handful of outings was dying to go down to the wet sand and in the water. Though the 250's coil is waterproof, the computer is not, nor are the coil:computer nor headphone:computer connections. The previous poster makes a good point about risking a drop or splash that could destroy the thing. And, again, it goes crazy anywhere near saltwater.
Anyway, my outings ended up fewer and farther in between since I couldn't go in the water. Recently though, my family chipped in and bought me a PI Pro as a birthday present. It works great in the wet sand -- recently dug out a dime and a penny that required knee deep holes to get to. As for underwater, I'm still anxiously waiting for some calm seas. The only drawback so far, is that I miss the discrimination and depth displays of the 250 -- the PI Pro just beeps... period. No separate sounds nor displays for metal type or estimated depth. But that's the trade off for the extra depth capability and the waterproofing.
So -- my advice, if you're primarily going to go to the beach, save up a little more money and get a machine specifically designed to deal with the wet sand and saltwater, because you're going to want one shortly anyway. You can probably find some used ones on line. Another way to go is to hook up with your local club and see if anybody there will give you some advice or even some stick time on their machines to see what's best for you.