Some totally fascinating info on drownings from the Center for Disease Control:
https://www.cdc.gov/drowning/facts/index.html
A 30" x 2" diameter foam swimmer's noodle tied tightly around the waist with a line threaded down the center hole is an extremely effective "pfd in a belt" plus it is an excellent swim training aid for swimming in 65-degree cold water, deep water, or rough water. It has enough flotation to provide a slight positive buoyancy for a 200-lb male.
Spend about $25 for a wet suit tee shirt, or wet suit farmer john shorty, and you are good to go swimming in water temps down to about 60-degrees.
And, as a general rule for boating ......
http://www.army.mil/article/223974/a...water_dont_mix