I'm thinking of going under some bridges & local diveing rocks in the foothills of Calif. & Lake Tahoe VIA Hookah & am thinking Excal...Can anybody tell me how the unit might respond in hot rock heaven??? Black sand??? I'm also wondering about the tone I.D. Is it similar to the Exp. & can you get a pretty good Idea of the target before digging...Say between lead, iron, aluminum, rings, silver & gold??? I'm painfully aware that to i.d. 100% I need to dig...but does it give you a PRETTY GOOD idea of what the target MIGHT be???