I have a White's MXT.  Decent on coin, relic and has a prospecting mode.Runs at 12 Khz, so is not as good as some higher frequency machines on small gold.  As an all around rig I think it is one of the better machines out there.  That being said, since you are near beaches, you might take a look at the MXT Sport.  has the features of the MXT and is waterproof in shallow depths. 

The MXT line also has coils from 4x6DD and on up.  I like the 6x10DDor the stock 9.5 concetric for general all around, and the 4x6 forhigh trash areas.

Garrett makes a simular unit as well, in about the same price range.

I would say the  Garrett AT Pro is one of the best all around detectors. If you get the 5x8 coil it will be a decent nugget hunter. But for a good coin, beach  and have the decent water hunter it is hard to find a mid range price to compete. No detector is perfect and there are better water machines but remember it has a lot to do with the user. Hope this helps and keep asking questions.