but, I think there is one pin-pointer that can be stuck in soft ground, because it has a metal point, but I don't know if it's water-proof.
The other one that is water-proof, is the vibra-probe, but can't be stuck in the ground to determine depth.
I am also thinking that the detector pro probe is prolly water-proof as well, but is a little more pricey.
I have found that the Treasure Mate has been the best one for me. I prefer this one not to determine depth, becasue the volume of the tone usually gives you a rough hint as to the depth, but because it can help pinpoint exactly where the target is if you don't recover it the first few digs down.
laterz
ed