welcome
just my 0.02.
im not a cheap traveler and im not the 1% traveler, but i try to be some where in the middle.
my 1 month trips cost me 5K per month for everything other than food. so its about 165 USD/Day. I say this so you can get an idea where that extra money could go for me.
I only did an 8 day cruise on the western part of the islands and it was my 1st time there. Never snorkeled before either.
our days were filled if we wanted to participate. No one forced us. I was motion sick when the ship was moving and ok when it wasnt.
but even with our days filled, there wasnt alot of people looking to party or go on some adventure. we did have some heat/humidity and for me it can suck some of the life out of me. So was tired after the days activities and most of the others were too. If there was any sun left, some were out sunning or reading (no internet unless we were in a bay).
the food was fine for me, but you have to remember, they have to cook for everyone at least on our ship. there were no people with any dietary restrictions on our ship either. And ive been around long enough to know even a hotdog or PB&J can be a 5 star meal if you are hungry enough. I never went hungry unless i was motion sick and even then, i always have some power/granola bars handy.
If you can afford what those ships offer you, go for it. As mentioned, you will all be doing more or less the something and breathing the same air and snorkeling in the same water. For me, id rather use the money to extend my days or for something else.
I have no idea on what type of guide you will get. Our guide mentioned that they do have to take tests and be qualified.
YMMV
good luck