We’ve done that excursion twice and it is one of our favorites of all time out of our 10+ Caribbean cruises. It requires that you be able to get in and out of the catamaran with fins in the middle of the ocean. It also involves a lot of time in the water, sometimes in choppy waves, so it is not for swimmers with no experience or endurance.
They can change the itinerary if the weather is not appropriate. You get two different stops for snorkeling, but the last time, we didn’t do the shipwreck because of strong currents.
They bring you back to the bus by cutting the motor and using only the sails. That’s a real fun bit, taking in the sun laid across the nets of the catamaran.