Nothing illegal going on. More of an etiquette thing. If I was at the beach (lake beach) during peak hours I don't want to bust out all the gear. Might be fun to just swim around in the shallows and try one of these.
I have the 580, I bought it in hopes of getting a water machine down the line. I use it as a pointer on dry land now and it works well the guys are right on about depth but is does pick up very small items at close range. the turn on by tilting seemed a good idea when I bought it but definatly slowes me down waiting for it to turn on and off my old centec is much faster gets as good a depth on large items but has a problem on the small stuff.
Wish I would have bought the pistol probe!