South of Belize City, the Placencia peninsula offers a few good snorkeling dive sites. During a Placencia snorkeling dive, you may encounter parrotfish, queen angelfish, squirrelfish and barracuda. Most of the action from Placenia is offshore to the east in the barrier reefs, such as Laughing Bird Caye.
To reach the snorkeling in Belize by air, fly into Belize City International Airport (BZE) which is located west of Belize City. Since there are few hotels near the airport and the airport is pretty far from the sketchy Belize City, you will want to arrive as early in the day as possible to meet your connection. There are two small inter-island airlines that serve many other destinations off-shore of Belize. Note, even if you reserve a specific inter-island flight at a specific time, only after you check-in with the inter-island carrier are you really assigned to an actual flight at an actual time. While there is a ferry service from downtown Belize City to some islands, there are only informal taxis (in personally owned vehicles) from the airport along slow roads thru run-down neighborhoods to the ferry dock, which is located in a very sketchy area. Hence, the ferry service does not tend to be a very popular option with tourists. When you are departing from Belize, the departure tax is included in the airline ticket, but make sure to verify.
Overall, Placencia is the 12th most popular snorkel dive spot of all 33 snorkeling dives in Belize.