Food & water. Bring more water than you think you'll need. You and your dog will both be in the sun more than usual.
Newspapers or a doggie toilet. Your dog probably won't get it right every time. Watch for their usual warning signs, accompany them as you would on a walk, and clean up any messes.
Doggie snacks. Always keep treats handy to reward good behavior on board.
A carrier, harness or leash. Local leash laws apply even at the dock, and health ordinances do not allow pets in marina stores.
A dog ladder or ramp. You'll need an easy way for your dog to get out of the water and back on board. A collapsible floating ramp mimics the shoreline and is easier for older or heavier dogs.
Proper paperwork. Up-to-date papers and vaccination records, just in case.
Boating with pets takes patience and preparation, but when you and your best friend are out on the water, you'll be glad you did it.