I have used JamaicaForADay.com (insert island instead of resort for a day.com, they are all the same company ie cozumelforaday.com resortforaday.com)
I have very mixed reviews, partly their fault, partly not.
My complaints, seemed like it took the bus a while to get going. When we finally got to our AI Sunset in Montego Bay (absolutely no complaints there, I loved that place!), there was a 1.5 hour line to pay for the rest of our day. So we only had so much port time to begin with at an All Inclusive resort, and at least 1.5 hrs is spent in line. I don't know if their credit card machine was down that day or what but it was soooo long. $70 is going fast...
The reason I don't place all the blame for them is that we had only paid deposits to book the day trip. We could have PIF and prob passed the line right up. But we didn't want to risk it because Carnival had already changed our port once on us, so we didn't pay anything more than the deposit just in case. We didn't know half our morning would be spent in line.
Then the bus driver says "meet back at 3:30, the bus is leaving." At 2pm, I say "let's go snorkel for 20 min" and out we go. I keep a very close eye on my water proof watch. I also think we have well over an hour anyway. We get out at what I think is 2:20 and one of our friends at the beach who is in our group says "hey girls, the bus is leaving." And he's super laid back, so I thought he was kidding. My husband has never, never been so furious. According to Jamaican time, it was an hour ahead (bus driver did NOT mention that!!!!) and basically we wrapped a towel on and got on the bus soaking wet and with my honey fuming.
Bottom line, we lost several hours of our all inclusive paid resort stay for that day. One of which because they couldn't process an entire bus load of people in less than 1.5 hrs (and getting the bus from port going was slow anyway) and then we ended up losing an hour at the end of the day too.
Again, not 100% of it is Jamaica ForADay.com fault but I wouldn't use them again. If it was me, I'd find my resort (I have nothing negative about that Sunset resort in Montego Bay, it had a lazy river and water park, great drinks and buffet) and then I would contact them myself and purchase a day pass directly with them and take a taxi there. Get your own transport so you don't have to wait for a bus to fill or for 40 people to finish paying and then get picked up an hour early than your all aboard time because other guests have an earlier all aboard time than you.
I can personally vouch for Sandals and Beaches in Ocho Rios because we had our honeymoon there and they are 100% perfect. There are a million beautiful AI resorts there anyway.
I wish I could speak better about the online broker, but our day pass just ended up being about 4 great, great hours. I would sadly cut out the middle man or find someone else next time. Their resort was great but it was so, so, so disorganized and a big fat time sucker. You can buy AIs from the cruise line. For $20 more, I could have had a guaranteed extra amount of time (not having to worry about the 1.5 line for everyone paying their day pass because it would have been handled by the cruise line) and we wouldn't have come back so early because it would have been only our cruise, not all the cruises with different all aboard times. It would have been well well worth it to pay $20 more through the cruise line, hands down. If they would have changed the port on us again, CCL would have had to refund our excursion if we would have bought through them.
This was one of the several (Belize being another) where booking outside of the Cruise Line was a bust. I know a lot of people say you dont have to, and that's true, but 100% of our cruise line sponsored excursions have been stellar, and I cannot say that about the other tour groups. This was one of the let downs...
Again, you might be fine, maybe it was just a weird day or something. But not a day I will be repeating.
We had good success with shoreexcursionsgroup.com tho!