14 CFR § 136.9

Except as provided in paragraphs (b) or (c) of this section, the operator and pilot in command of commercial air tours over water beyond the shoreline must ensure that each occupant is wearing a life preserver from before takeoff until flight is no longer over water.

The operator and pilot in command of a commercial air tour over water beyond the shoreline must ensure that a life preserver is readily available for its intended use and easily accessible to each occupant if:

The aircraft is equipped with floats;

The airplane is within power-off gliding distance to the shoreline for the duration of the time that the flight is over water; or

The aircraft is a multiengine that can be operated with the critical engine inoperative at a weight that will allow it to climb, at least 50 feet a minute, at an altitude of 1,000 feet above the surface, as provided in the approved aircraft flight manual for that aircraft.

No life preserver is required if the overwater operation is necessary only for takeoff or landing.