And at La Isla Bonita, police were called to cool heads between two rival water taxis operating next to each other. Tensions flared over the weekend when Giovanni Marin, the owner of the Tackle Box Pier, reportedly had a misunderstanding with the San Pedro Belize Express Water Taxi, which was using Marin’s dock. Marin reportedly kicked them off his pier and welcomed back old time partner, Caye Caulker Water Taxi Association, to do business from the location. Almost a year ago, things were in the reverse, when Marin parted ways with the Caye Caulker Water Taxi group and helped form the San Pedro Belize Express. The new agreement between Marin and Caye Caulker Water Taxi Association apparently got in the ears of a few members of the San Pedro Belize Express group and overnight the group removed themselves and worked out a deal with Ambergris Divers. So when they set up shop next-door this morning, the situation became volatile and police were assigned all day to the location to keep the peace. Meanwhile, San Pedro Town Board is said to be reviewing the trade licenses of both water taxi companies.

IMHO, services of this sort become "public transportation" as soon as people depend on them in significant numbers. Routes should be assigned, and rates managed more or less like bus companies elsewhere.

I thought they were specifically licenced as Public Transport or something like it?

OK - I'm not talking about the name of the license, but rather the method of regulation so carrier and public alike have something reliable and workable. It is not uncommon to assign exclusive routes to a particular carrier, and in exchange for that to require that they run not only at peak times but at slower times too in an effort to serve the public.
Perhaps there is already some mechanism in place, but it sure doesn't look like its in practice.