The Coast Guard and the Federal Aviation Administration regulate the vessels that may tow parasailers and flight activities, respectively. The Coast Guard regulates small passenger vessels and other vessels that conduct parasail operations. This does not include oversight of parasailing equipment, safety of passenger(s) aloft or interference with aircraft or banners being towed by aircraft. The FAA regulates parasail flight activities as well as aircraft and banners towed by aircraft. MSIB 002-19 addresses Navigation Rules relevant to the operations of the vessel pulling the parasail wing and provides information to promote safety while operating with passengers aloft in the vicinity of aircraft that may or may not be towing banners.
Source: USCG
Link: 3/6/2019: MSIB 002-19 – Parasailing navigation rules and flight safety