I had an Infinium for about 3 weeks. I gave up and took a refund.
Actually it is a very sensitive machine. I wanted to use it in the water and at that time the only coil available was the 10x14. There is lots of Radio Frequency in my area which made the Infinium difficult to tune.
With the 10X14 coil it was nearly impossible to use in the water. That coil did work well over sand. I found small gold that my other 4 detectors would miss. It would locate small gold ear rings, charms and chains at the expense of spending many hours sorting out the tiny metal junk that we normally hear. Extreme sensitivity has it's down side. I wanted the larger chunks that had value and got tired of looking for thins that were tiny.
The shaft is a wet noodle with the big coil. annoyed me to no end.
It might possibly be a fine machine with 8 inch coil.
Why would any good company advertise a machine for underwater then not supply proper headphones. Garrett goofed there. You should have the choice with out springing the extra $100.
As of a couple days ago they were out of water headphones and only guessing they would be available in a few months. When the Infinium first hit the market they said a 8 inch coil would be available. It took a very long time for that to happen.
It is a fine looking machine. Garrett is a good company. Give one a try and then give us a report.