There are two water taxi services between San Pedro and Chetumal (see websites for schedules & fares):
a) San Pedro Water Jets International:http://www.sanpedrowatertaxi.com/index.html
b) San Pedro – Belize Express:http://www.belizewatertaxi.com/
One departs at 3 pm, and the other departs at 3:30 pm. Trip time: 90 minutes.
The San Pedro – Belize Express Water Taxi has a connecting water taxi from San Pedro to Caye Caulker.
It's about 4.5 hours from Playa to Chetumal, so get an early start -- try to get to the water taxi office before 2pm.
In Chetumal, water taxis use the main pier, “Muelle Fiscal”, which is close to the big Government building, “Palacio Gobierno”, at the waterfront. On my BelizeBus site, check the map of Chetumal for the locations of the ADO bus terminal and the pier. The pier is also visible on Google Earth.
If arriving in Chetumal at the ADO bus terminal, there is (or was) a little booth inside the terminal where you can get water taxi information. You could probably buy a ticket there, but you might get pushed into an overpriced taxi. I’d just go outside to get a taxi, and buy a ticket at the pier.
It’s about 3.5 km from the ADO terminal to the pier. A taxi should take about 10 minutes, and cost about MX$15 (that’s pesos). The taxi driver might not know about the water taxi, but he/she will know the pier. Write it down if you can’t pronounce it.
Get to the pier at least 30 minutes before departure time for immigration processing. There is no exit fee/tax when you depart Mexico. No fee upon entry to Belize (you pay to get out!).
When you get to the pier, ask for the price at both companies -- sometimes they will give a discount if they see you going to the other office (the offices are around the corner from each other).http://belizebus.wordpress.com/