Do not drink and swim.

Many resort-style beaches may allow you to consume alcoholic beverages while enjoying the sun. If working on your suntan is all you intend to do during your day at the beach, go ahead - relax and sip away (though you should still be careful to not become dehydrated, and you should not drive after drinking on the beach all day!) But if you're thinking of cooling off in the water, you should definitely wait until after your swim to indulge. Alcohol is potent by itself, and sitting in the sun - especially if you aren't used to it - tends to dehydrate you further and heighten the effects of alcohol. Inebriation will change your perspective on your environment, and will slow your reaction time. Much as you would not drive or even run a race while intoxicated, you should swim only when sober to help ensure your safety while ocean swimming.