Make sure that everyone is on the same page regarding standards, when you book with friends.
While not everyone in your group wants fine dining on board the vessel, make sure you go for a well-maintained boat with a professional, experienced crew and good chef. If you have friends that have particular dietary requirements or allergies, let them know in advance. Ask to stock up with your favourite bar drinks.
Check what equipment is on board for fishing, snorkeling, diving, …. You might want to rent extra equipment or bring your own. If the boat does not have your favourite board game(s), you might want to take those too. Don’t forget your favourite book, dvd and music. While you will be in the water surfing most of the time, it’s good to prepare for the relaxing times in between or the days that the surf should be less consistent.
It’s worth considering add-ons like a photo or video service to document your trip, especially when you are travelling as a group. These details can make all the difference. Good preparations are most important and will provide you with the best memories until long after your trip.