Certification: If you decide to hold your function on a boat, make sure that it is Coast Guard certified. This ensures the safety of all concerned, and also avoids all kinds of legal, tax, and liability problems.
Capacity: Never allow the possibility that more people 'might' attend than the boat can legally accommodate. Coast Guard certified boats have a maximum capacity. Make sure you have an accurate guest count - it would be very embarrassing to have to leave someone behind.
Catered events: Many of the boats boats suitable for events are known for their fine dining. You'll be surprised by the variety of choices available to you, both formal and informal - even theme parties.
Preferred vendors: Be sure to ask whether the company you select has a list of preferred vendors they work with. It is often easier to have vendors who are familiar with the boat's set-up than to have someone who has never worked on the boat you have selected. Also keep in mind that some companies only allow you to work with vendors from their preferred list.
Budget: When reserving a boat, make sure you have a detailed estimate of the costs and time involved, and the charges for any additional hours.
Boarding and sailing times: Be very clear with your guests about the exact boarding time. It's best to allow at least one-half hour between the boarding and sailing times. Remember, if you hold the boat because someone is late, the clock is ticking, and your budget will suffer.
NOTE: If you plan a special occasion on a boat, be careful when selecting footwear for your bridesmaids and yourself; in most cases, you and your wedding party will be walking across a dock to get to the boat. Stilletto or high heels can easily wedge themselves into the cracks in a dock. Also, boats do rock back and forth...high heels may make balancing difficult!
A final thought: When planning events aboard a vessel, it's more important than ever to double-check everything, and order plenty of food. Once the ship sails, there's no running to the store!