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I can add with how it is here in Sweden: While the boat is moving, the driver or anyone onboard that is essential to its handling, are not allowed to have over 0.2 per mille of alcohol in the blood. Then you can be convicted of the "soft" form of boat-drinking. If they have over 1 per mille, they are convicted of the "tough" form of boat-drinking.
The police uses boats like the one below to chase you down. Of course you should not drink when drivning your boat, but if you are out camping with it, it happens that you have to move the boat at the evening if the wind shifts after having some glasses of wine, then you may be in trouble.