Bless your soul for being 85 and still able to snorkel! This vest would work for snorkeling but you will have the bouyancy primarily around your midsection. It is personal preference where you would like the bouyancy. The other dependent factor is if you use your arms while snorkeling or just kick with your fins and keep your arms close to your body. If you use your arms this life jacket would give you exceptional freedom of your ams. This is a well made well designed jacket.
My experience is they run large. Two females in my family are 5' 6" , 125 pounds and they prefer the small vest vs. the medium. I am 6' 2", 200 pounds and the large is plenty big on me.
Enjoy your snorkeling!
Hi Craig, Thanks so much for your answer. It sounds like this will be perfect. I will think of you when I am snorkeling. Ginny