I have a few questions on this machine. Looking for some settings from folks who use it. I am also looking for inf on digging in the surf when to dig and where in the water in the wave where? I also would like to know what the knob in the middle is for what does it do for me at a beach etc. I leave it off and the machine works fine. I just click it on and still works OK turn it up and its like I have no depth? This thing digs deep and everything my shoulders are sore. I am seriously thinking of selling it too much digging for me.