It doesn't discriminate like a regular VLF machine. You can apparently sort of tune out a couple of items, but at the cost of losing great depth. The Sea Hunter is a very capable machine, which can punch through most areas with a high or low pH and salt content, where a VLF machine struggles. The Sea Hunter, when used in the right locations, used as a PI should be used (little or no disc) and by a person who isn't afraid to dig all (most good H20 hunters do) targets should do very well. The INFINIUM, a step up from the Sea Hunter has it's own forum.......
http://www.findmall.com/list.php?62
"A Garrett Sea Hunter was used by famed treasure hunter, Mel Fisher's team, to find silver and gold from the 1600's Spanish treasure galleon "Nuestra Senora de Atocha" off the Florida Keys in 1985. Without significantly degrading the sensitivity of rings and coins, the Sea Hunter Mark II can eliminate most pull tabs and foil in Discrete Elimination Mode. It's a favorite around the world for its ability to ignore salt water."
http://www.melfisher.com/default.html