We were on the Golden Eagle in July (with Princess and I have to agree with Elise - we thought it was the best excursion we had ever taken.
On the way out to the Island (Tintamar - weather permitting) they served Mimosas, soda and juice. The trip out to the island was a lot of fun as the captain gave some history and described points of interest. Once the catamaran is docked, you can hit the beach, snorkel (they have the equipment on board) or use floats (the noodles) in the beautiful water. You can also remain on board.
On the way back, they provide sandwiches and snacks as well as drinks. The dock in Phillipsburg so be sure to bring some spending money if you plan on doing any shopping. This way you don't have to go back to the ship for money and pay to use the water taxi (like I did
One thing to keep in mind is if the weather results in high swells, those prone to sea sickess will want to have their patches on - or should sit towards the back of the catamaran for smoother sailing. We had high swells and some people were a bit quesy, but those who were prepared we fine. They also have bonine on board for those who need it and I hear it works fairly rapidly.
If you have any other questions, please feel free to ask. Happy sailing!