I just learned to snorkel on our last cruise lol I think my biggest fear is sharks and big waves (first one is slightly irrational, I know). Do you have to bring your own snorkel equipment on the PE, or do they provide them to you? I'm sure every PE is different, just not sure if we need to purchase/pack them or not. We were looking at:
https://disneycruise.disney.go.com/port-adventures/tortola-virgin-islands-schooner-sail-away-swim/
or
https://disneycruise.disney.go.com/...-virgin-islands-treasure-island-swim-snorkel/
I will look into Trunk's Bay! Did you do it on your own or part of a PE? Trying to decide if the cost of having everything done for me is worth it, or if we can easily navigate our way there.
I totally get both of your fears! Generally, if the seas are rough, they shouldn't be snorkeling there as it's not comfortable for even experienced snorkelers. All of the excursions provide snorkel equipment (most of what I've seen has been nice equipment, not crap).
One thing you might be more comfortable with is getting a "dry" snorkel--at the end of the snorkel is a valve that closes when water/wave hits it so that you don't suck down a lung-full of water. Makes snorkeling
so much more fun and enjoyable. You can either buy a mask and snorkel set or get one with fins (fairly inexpensively at Costco/Sams). Here's a picture of one type of dry snorkel:
US-Divers-Total-Dry-Snorkel.jpg
I think whether or not you bring your own snorkel equipment is just a personal decision. My family tends to pack our own, although one year, my son had outgrown his fins and I didn't have a chance to buy him a new set, so he just packed his snorkel and mask and used the excursion providers fins. My parents will occasionally just pack their masks and snorkels and use the fins on the excursion (on a cruise) or pack everything if they're going to their condo on St. Maarten. My mom has even gone so far as buying her own snorkel vest as she likes having her own (and all excursions, except the privately booked, make you wear one).
Both of the excursions you're looking at look fun, although if Rebel Yell is planning on snorkeling at the Caves, it's really really beautiful and had lots of things to see. Plus it looks like there would be less people on the boat (ha! I'm all about less people)!
We didn't actually get to do Trunk's Bay. We ended up booking a private sail boat and going snorkeling. But if we didn't get a good deal on our excursion, we were planning on doing Trunk's Bay on our own. It didn't look too difficult to do on your own.