The problems come when it is the harbour authority / water men that are drinking and then working on the water. I know of at least 1 commercial ferry driver who was drinking and then operating boats with paying passengers on board. This is a shocking state of affairs and I completely back this regulation to the hilt. On the other hand is drinking a if you have a sober skipper a problem. If not what about yachts on moorings or at anchor. or a booze cruise. could go over the top or could be good. I suspect that where you are in the country will play a large part in how well enforced the regulation will be.
No drunks on boats =
but no moderated amount of red wine =