BoatU.S. has a whole section devoted to boating with pets. Here are their tips on preparing your dog or cat for a cruise.

Make sure your pet is wearing a flotation device, preferably one with a handle so you can lift their head above water or help lift them out of the water.

Make sure dog had identification or has been microchipped.

Put the pet's bed or bedding in a quiet area.

Carry a fresh water supply and keep it available at all times. Avoid allowing your pet to drink the local water.

Carry enough food to cover the trip plus a couple extra days. Limit the dog's intake prior to the cruise. After 4–5 hours give your pet more food.

Make sure to carry a supply of any medications that your pet may be on.

Keep a long handled crab or fish net within grabbing distance on deck to retrieve pets that fall overboard.

For cats hang a strip of carpet overboard in case they go overboard. They may be able to grab it and climb back up.

Make sure your dog is exercised by swimming or running around the deck. Bring floatable toys for the dog to play with and also chews.

When on land never allow your pet to roam off leash, never allow your pet to go visit with a strange dog. Clean up and properly dispose of any feces.