Easy does it. Drink plenty of water. Even partial dehydration lowers your body's resistance to the stressful factors caused by diving and the boat ride. Take lots of water with you and drink often. Do not drink alcoholic beverages for several hours before a dive.
Alcohol tends to dehydrate the body.
Its other symptoms are not desirable either when diving. You may feel tired and unalert from just a few drinks, two qualities not conducive to safe diving. If you do plan on drinking, make every third drink a glass of water. It will reduce dehydration and your chances for a hangover. Avoid gasoline or diesel fumes.