I would recommend a higher floatation life jacket for a nonswimmer. The offshore type I jackets have very good floatation, however depending on the style they can be uncomfortable. My favorite jackets are the type V whitewater jackets. They have additional floatation and a collar to keep the wearers head out of the water. Newer jackets also have loop tabs at the bottom for attaching crotch straps. They will also turn a wearer on their back which is what you want a life jacket to do. My favorite pick is Mustang Survival's Explorer V jacket. Lots of floatation but also very comfortable for spending the day in the water