All persons on an underway vessel must be in a personal flotation device except when they are below deck.
Boat Length
In Massachusetts boating laws and regulations apply for vessels of all lengths
Compulsory PFD Requirements for Massachusetts
Children under 12 years must wear a type I, II, III, or V USCG-approved life jacket. The PFD should be worn at all times when the boat is underway. It should also be in good wearable condition and fit properly.
Exceptions from wearing PFDs in Massachusetts
It is not necessary to wear a life jacket when the passenger or boater is below deck.
Disclaimer: The information presented here is meant to be a general reference for educational purposes. Please check with your state for the most up to date information and any current changes in the laws. Source: BoatUS