Type V -inflatable or special suit type, buoyancy varies. (Type V must be worn when boarded or inspected to count toward requirement.)
Type II -near-shore, less buoyancy than type I
Type III -inland/max comfort, type II buoyancy.
Type IV -throwable unit for calm water rescue.
What You are Required to Carry (minimum)
Boats less than 16', canoes & kayaks One type I, II, III or V for each person on board.
Boats over 16' One type I, II, III or V for each person on board and one type IV throwable.
All PFDs must be USCG approved, properly sized for the passengers aboard and worn or readily available.
In NY, anyone on a jet ski, being towed behind a vessel, or under 12 years old must be wearing a PFD. Exception for children under 12, only if they are in a fully enclosed cabin.