Hobbes, how do you like your Surf PI Pro, most of my hunting will be in waist deep surf were I could keep the box out of the water but I think it will be a matter of time before it gets wet. Do you use yours in the surf a lot?
That's where I use it pretty much all the time, from knee to chest deep water. I do some wet sand searching as well, but mostly, I like to search in the water.
The machine is waterproof down to 100 feet, so don't worry about getting it wet in the surf. Just like with anything you use at the beach, take care of it by washing it off with fresh water after each use, and it should last you a long time.
Because it's a PI, you will dig more trash. That's just the nature of using a PI machine. The salt water corrodes iron quickly though, so it's not as much of an issue in the wet sand and water. You can learn to identify some iron, such as wires, nails, hairpins and fishooks, and avoid digging them if you like. You'll hate a PI in the dry sand or at a freshwater beach, though.
The only complaint that I have about the machine, and again I think this is the case with most PIs, you will hear a threshold change as the swells go in and out if you have the gain set at the optimum level. It's still quite usable, though.
Overall, I really like the machine. Right now, I can't think of another PI that I'd buy, unless I were to have an extra $2,500 laying around to purchase an Eric Foster special.
Like I said, this is the only waterproof machine I've used, so take my 2¢ for what it's worth.