In addition to the two water services noted in the previous post, there is a third service...http://www.cayecaulkerwatertaxi.com/
I think this is the website that says "hourly runs", BUT the San Pedro Water Jets International water taxi service operates from the same terminal as CCWT.
While neither service offers hourly runs, the combined schedules of the two services amounts to an almost hourly run from the terminal
All websites show the full schedule in both directions, you just haven't found them. On the CCWT site, there is a "Schedule & Departure" "tab"... click the "Learn more" link at the end of the text.