Ahoy Patricia!
I'm looking forward to another magical sailing onboard the newest gem in the Disney fleet as well! I'm sure, like me you can't wait to create more special memories when your family casts off for an Eastern Caribbean cruise.
I'm glad you asked this question because I was able to reach out to my friend in the Port Adventure department for assistance. He informed me that all snorkeling tours have lifejackets other than the snorkeling vests that you will be able to use on your excursion. He recommended
Captain Nautica's Snorkeling Expedition in St. Thomas because the vessel is smaller and you will be able to receive more attention from the tour operator. Since you aren't a strong swimmer, he also suggested you send an email to the Fantasy Port Adventure Team at dcl.shore-excursion@disney.com once you are booked so they can inform the tour operator of your request. If you forget, you can stop by the Port Adventure desk once you are onboard.
I hope this is helpful, Patricia. If you have any other questions, please let me know.
Have a magical day and good luck with your plans!
Nancy