Detectorpro UW8 works like a Pirate Pro and a Wader.
UW8 is waterproof, Pirate Pro and Wader is not but the wader can change coil between an 8" and a 10".
I've used a Wader to chest deep, no good in air test but fine on wet beach, seem to like Silver.
All above can disc out hair pins without loosing depth on our 5 coins, something a PI have trouble doing.
There is a number of Youtube video on the UW8.