I've the opposite experience with the 2 sharks I own. For multiple years, not a problem, other than a hole in a coil that I wore into it myself on shells without a coil cover. You will continually hear talk of "no iron" with the excal, what you don't hear about is the tiny tid bits of aluminum foil, gum wrappers, pop tops, pull tabs, rivets, and twist ties, that it loves to find. To this date, i've yet to find a single piece of aluminum foil or twist ties with my Sharks, yet have no problem finding the most minute of gold. Likewise, i've not had issues with depth. Any deeper, I would need an excavator. To the OP, I don't care for the wagon wheel, overly buoyant coil myself.