Hi Steve, say, did you ever try a Tesoro Stingray? I bought their first model and used it to detect swimming holes in creeks and rivers. It seemed quite sensitive and would find very fine gold chains. The first model's groundbalance was in the case, so you obviously couldn't adjust it underwater. However, I believe their latest model has an accessable adjustment. It wouldn't find as small of pieces like the GB, but it should be comparible to the Minelab. Also, Tesoro's warranty is really good. Once I got a leak in the case and had to send it back to the Mfg. Had it back in two weeks with new case, coil and spit shine. That was 3 or 4 years ago so I don't know if they're still that good. By the way, congratulations on making a waterproof casing, that is no small feat! Regards, RockChuk