If you want to detect wet sand or in the water, stick to the multi-frequency detectors like the explorer or sovereign, they won't be water proof, but it will be hard to get the best of both worlds on that budget. Whilst the AT Pro is waterproof, it will not handle the salt anywhere as good as a multi frequency detector, nor get as gooder depth.
As soon as you look at waterproof detectors that suit the beach, you will tend to pay a premium for the privileged, thinking of detectors like the Minelab CTX and the Excalibur. Plus you will find it hard to purchase a detector that can competantly cover all bases, better off sticking to dedicated gold detectors, waterproof/underwater detectors, and coin shooting specific detectors. People often buy one general purpose detector thinkng that it can cover all aspects of detecting, only to find that it is compromised in many areas - jack of all trades, but master of none.
Other options include a second hand Garrett Infinium, being waterproof, pulse induction, good for gold and wet sand/water detecting, but not the best detector for the park. Then maybe look at a second hand Sovereign or Explorer for all other areas.
If you discount the gold detecting and want to buy from new, something like the Explorer will cover parks, dry sand, wet sand, and shallow water hunting, and will competanly do 3/4 of what you want out of a detector. Do remember that the Explorer usually sits at a higher price point than the current Safari model, so the $970 pricing is pretty good.
