Fabian, the GP series detectors are very noisy in wet sand; I say avoid that at all cost.......if "thin section gold" means chains, PI's have trouble here.....PI's will detect thin targets, but they must be solid ....
Jennifer, the Excal is designed for in the water use....if most of your hunting will be water's edge or the dry, the weight of the machine might be something to consider, as the Excal is heavy....great for all types of gold objects, great discrimination if that is what you want, but you lose depth to the PI's.....
In places where there is at least moderate mineralization and without air traffic the Garrett Infinium is worth a look......a waterproof PI with good audible discrimination (for a PI) and depth superior to any VLF......better used at water's edge and the dry.....in the water it is more noisy than the Excal.....interchangeable coils (8" mono and 14 X 10" mono), both of which work well at the beach.....
PI Detectors
Aquasearch SS V.2 is an option (I am just learning how to use it, so no comment yet)
Whites Dual Field.....good depth......handles mineralized sand well.....the pro's I know love this unit in Southern California
Tesoro Stingray......handles mineralized sand well....easy to use, reasonable price, but lacks the depth of other PI's
Hope any of this helps, Jerry