I believe the last water taxi that goes all the way to San Pedro from the marine terminal in Belize, leaves at 4:30 p.m. It is possible to make it to the boat, and I have many times-coming in on those afternoon flights, but if there are any delays, you will be stuck in Belize City overnight. --Lee www.caribbean-colors.com www.cybercayecaulker.com
Yes, arriving at 3Pm may be pushing it. Taxi to the marine terminal is about 20 minutes (and about $20) so if you get delayed or customs takes long, don't chance it. Water taxi is 1 1/2 hrs and costs about $15 pp one way.