As far as I know, there are still two water taxi companies providing service between San Pedro and Chetumal:
a) San Pedro Water Jets International:http://www.sanpedrowatertaxi.com/index.html
b) San Pedro – Belize Express:http://www.belizewatertaxi.com/
Passengers are requested to be at the pier 30 minutes before departure.
Last year, the departure times did not change when Mexico switched to DST, i.e. they still departed Chetumal at 3:00 & 3:30 pm Chetumal time.