To give you a bit of an insight, the extreme tour takes you all the way around the island, stopping off at some of the most stunning locations the Island (and possibly the Caribbean) has to offer, which are only accessible by boat. Parts of the trip will be done at speed (hitting 45 knots or so on the flat Caribbean side of the island), but the gentle Atlantic swell on the east side is taken a little more leisurely, and always in comfort. The boat is definitely fit for purpose and given the limited numbers on the trip you feel like you're getting quite a private experience.
On board will be a mix of people from all over, and of all ages, although on the trips I've been there weren't any young families, but I think this must be as I tend to travel outside of the school vacation periods; plus if I was around 8-12 (and upwards) I'd have loved this. Also on board are the captain and two crew members, each of whom are very knowledgeable of the island, fun and charming. As you go around they will give you some history of the island, including English Harbour and Nelson's Dockyard, and also fill you in on the properties of the rich and famous. You'll be very well looked after throughout, the food is great and you'll be well-watered (the rum punch comes out towards the end of the tour, after the activities).
So, if you've been going to Antigua for a while and haven't done this - book up! You'll no doubt see some awesome spots you haven't seen before and I'm sure you'll learn something about Antigua (even if you think you know it pretty well - like I thought I did). If you're going for the first time and take the tour you'll be way ahead of the game - plus from the boat you'll also be able to plan the other beaches you should check out during your stay (like Halfmoon bay) and get tips from the guys on board as to where else is particularly worth visiting (which you may not get in a guide book/travel brochure). And if you're just visiting for the day this is a no brainer - you'll avoid the crowds and the corporate charters that barely scratch the surface, and see the best of what the island has to offer.
I've recommended this trip to all sorts of people - mates on a 'girlfriends have no holiday left, reckon we can get a way with a week in the caribbean kitesurfing?' trip, friends on their honeymoon, and my parent's friends, and they've all come back raving about this. You won't be disappointed.
Many thanks to Captain Ross, Trevor and Serge for the last trip.