Links or pictures, Andre? Around here you are required to tarp up and vacuum sand.. I've never seen anyone power-wetsand but it does sound like a great solution...... we'd probably have to catch the effluent somehow....
No, not power wet sanding - wet sanding with a sanding block on the end of a broom stick, not unlike sweeping the floor. Sorry, I am unable to get my kit out to show you because we're between houses and most of my gear is in storage. I'll try and describe the kit.
A plastic pad that is on a swivel that takes a third of a standard sheet of water paper - like this:
The black underside is a layer of neoprene foam.
Then I use the thin plastic tubing commonly found in home mini-irrigation systems taped to the broomstick and two nozzles that are drilled and screwed into the pad. Then when the water paper goes on, two small holes are made in the paper to coincide with the nozzles. The whole contraption is connected to a slow running garden hose.
Most marinas in New Zealand have water traps that separate the bad stuff from the water which is then recycled. But they also have "dams" which comprise a 6" tube made of canvas that you lay around the boat and fill with water. This traps 95% of the cuttings that are washed off the boat and tomorrow when it has reverted to dry powder, one simply sweeps it up and discards it.
So now you simply stand alongside the boat and scrub the bottom. The water flowing through the nozzles/paper washes away the swarf and keeps the paper cutting and the paper thus last a really long time before becoming dull. Yes I know it sounds like manual labour but trust me it goes really fast and does a great job. It is definitely far easier than using a machine, no matter how good the machine is. I know because I tried a machine once and will never go back there.
Tell you what, my boat is coming out for an anti-foul in the next wee while - I'll get my wife to make a short video to show here. In the mean time I hope the above description makes a little sense at least