when you are on or near the water always have a PFDs (often called lifejackets) or a suitable buoyancy aid. They must be worn at all times of heightened risk. This may include, for example: rough seas, non-swimmers, alcohol consumption, emergencies and distress.  It is compulsory for a PDF to be carried on all recreational craft.

How Many PFDs Do I Need?

You must have at least one, wearable PFD for each person onboard, and it must be the appropriate size. It is also wise to have throwable device (Type IV PFD).  Mandatory Safety Equipment
 

A wide range of PFDs is allowed in the rule to suit all types of boating activity. The skipper must ensure that a correctly sized serviceable PFD is available for every person on board. See PFD Basics

In some sports and ceremonial events the PFDs may be carried in another boat which stays in the immediate vicinity.

 size. If your boat is 16 feet or longer (generally excluding canoes and kayaks but check your state's regulations) you must also have one