Just been informed by the marina that we're currently at that they have been "certified" as a Maryland Clean Marina..with that "divers will no longer be permitted to perform in-water cleaning of boat bottoms.."
My contention is what was in the water stays in the water..cleaning a haul in the water is generally no different than hauling the boat out of the water..unless 100% of the particulate from power washing is collected..don't see that happening.
Bottom SCRUBBING when you use ablative paints is probably BAD for two reasons:
1. It unnecessarily and prematurely wears away the paint
2. The paint particles that have been scrubbed do no good in the environment
Im located on the Upper Eastern Shore of the Chesapeake. I used to use Micron CSC .... recently the water condition there became sooooooooo foul (turbidity that you can 'walk on') that Micron CSC no longer gives protection - if the boat isnt used every FEW DAYS a thick slime would form on the hull; and, the barnacles apparently 'anchor' themselves first in the slime to gain a foothold, and then eventually attach directly to the Micron CSC. The result is that Thousands of Barnacles were attaching to the hull (mostly 2-3ft. down from the waterline, down deeper on the Prop/Rudder, etc. - probably due to the electrolytic action of the running gear zincs).
Since Slime seems to be 'new' cause of enhanced hull fouling, Ive changed to Micron Extra (anti slime coating) which seems to be 95% effective in keeping the slime off the boat bottom; less slime has promoted NO barnacles.
With all ablatives you MUST 'move' the boat or keep it in an area where the water is MOVING - go sailing often .... OR when slime does begin to build, simply go out and anchor, take along a large rubber 'squeegee' (& affixed to an 8 ft. long pole) used for cleaning WINDOWS. From your dinghy you easily 'squeegee' off any accumulated slime, doesnt disturb the ablative paint hardly at all (very little 'red' in the water when you 'squeegee') ... and then go sailing.
In the Carolinas where slime & 'slime + barnacles' seem to be an especially bad problem, Ive noted that many boats are now using an ablative only 2-3ft. down from the waterline and then using a hard bottom pant below that. Many seem to be using Teflon loaded hard paints such as Baltoplate or VC17.
As regards the 'usual' prop barnacle fouling, Ive been using Petit Zinc Rich Barnacle Barrier with moderate success. Ive also noticed for quite a long time that boats that have lost their zincs do not have barnacle problems on their props - probably due to the electrolytic action between the prop metals and the seawater. Im going to experiment with NO prop zinc (on a huge Max-Prop) and rudder shafting, etc. ..... and when in my slip, etc., simply 'hang' a 'guppy zinc' over the side but electrically connected to the boats bonding system .... so I get full anode protection, keep the barnacles away from the prop, etc. - you have to make sure that the propshaft is somehow electrically connected to the boats bonding system to do this properly.
I have a 'high suspicion' that barnacle infestation STARTS with attachment to the prop/shaft and then the barnacles 'propagate' to the rest of the hull from that 'vector source'; and, if I minimize the barnacle attachment to the prop, etc.; then, the rest of the hull wont see much if any 'infestation'.
hope this helps.