My husband and I spent two weeks at Aquamarina this year and 5 days there last year. We were disappointed that they had changed management and become more corporate (I also thought it tacky that they added new rooms overlooking the cemetary). With that said we really like the rooms and location of this hotel. I think we stayed in room 207 this year. It's best to be in the suites on the 2nd or 3rd level in the most beachfront part of the hotel. We had to sit through their time share presentation this year but it was worth it for the free diving/snorkle trips. We let then know that we were definitely not interested in a time share and they were still nice to us!
They have a nice clean pool and lounge chairs on the sand beach in front of the hotel. There is a new dock in front of the hotel but it wasn't my favorite area for swimming. I'd encourage you to checkout the swimming areas to the south - the pier at Ramon's Village is a short walk (good place to spend some quality time sunning, reading, snorkeling & swimming)and farther south (about a 15-20 min. walk) Banana Beach & Caribe Island. To the north the pier in front of the Blue Tang is a great spot to swim.
I don't think the restaurant at Aquamarina is anything special. Our very favorite places to eat are Jam Bel Jerk Pit (rooftop deck is a great place to dine), Papi's Diner (a local favorite), Estel's (right on the beach - great for breakfast & lunch), Casa Caramba, Ruby's (popular for pastries, johnny cakes)& Mannelly's (homemade ice cream). There are so many quirky little places along the beach and in town. It just depends on what you like. We stay away from the San Pedro restaurants that bill themselves as "fine dining " i.e. $$$$ restaurants as they tend to be disappointing. It just depends on where you feel more comfortable.
About side trips... Some fun things to do are to rent bikes (or a golf cart) and explore the north island. You get there via the hand ferry. Check out the Palapa Bar(open mic on Sundays). Capricorn Resort is a beautiful spot for a stop. Their restaurant is more expensive but well worth it for a special evening. Snorkle trips to Hol Chan Marine Reserve and Shark Ray Alley are a must. We also took a water taxi to Caye Caulker. We took a snorkle trip to their Shark Ray Village, sunbathed and had lunch at Rasta Pasta. Depending on how long you are going to be on the Caye,whether you dive or enjoy boating... You may want to take a day trip to the Blue Hole/Lighthouse Reef/Half Moon Caye. If you are interested, go with Amigos del Mar as they have the biggest boat. Being on a large boat for this trip is much more pleasant. This is a great trip even for a snorkeler (like myself).
Ambergris Caye is very laid back, everyone is friendly and the only annoyance is the influx of time share salespeople. There is always live music at some bar in the evening. We thought we would take a side trip to Tikal or explore some other areas of Belize but San Pedro is just too wonderful! Who ants to leave the beach? If you don't already have it, I recommend you get the Lonely Planet Belize guidebook. Have a reat trip. I am so jealous!!!