I am 20/450 in both eyes - I believe that's twice the threshold for legally blind. I'm 20/20 in my glasses. Suffice it to say I never want to be without corrective lenses on the water, or I can't see ANYTHING. Not the boat in front of me, and certainly not the best line to take.
I bought a pair of Rec Specs with prescription and tint.
These are not only perfect
for me in boating, they are hands down the most durable and well made pair of glasses that I've ever owned, regular or sporting. I got my prescription put in, and it's thin (which is hard to do when you're blind as a bat), and the cost of lenses and frames, out of pocket (I was not able to use insurance on this pair) was under $300.
I went kayaking about 3 times per week last year between Memorial Day and Labor day, plus I wear them as my general purpose sunglasses. They are "impact resistant" and the lenses that go with them for sporting purposes are "scratch resistant."
To date I have had zero scratches, zero cracks, zero impediment to my vision in any way (save fogging, for which I periodically use a defogger as I paddle). They came with a built-in strap that has never come off in any sporting situation, mountain biking or kayaking (and I'm not the best in either).
I cannot recommend them highly enough, which is why I put the link in.