The best sailing sunglasses must made with polarized lenses and tough frames. In details, Sunglasses polarized can shield your eyes from glares from water surfaces. Besides, the lenses shall laminated to help you read a GPS or chart plotter. Besides, the lenses color is also important for comfortable wearing. And grey and amber colored lenses are considered the most comfortable choices. In addition, tough sunglasses frames are needed. The frames must be very durable, unbreakable and strong.
If you want to get sunglasses for sailing, I think polarized sunglasses are a good choice. polarized sunglasses can help reduce the glare reflected from the surface like water, snow and glass. When you go sailing, polarized sunglasses can help reduce the glare from water surface so that you can see things underwater clearly. The color of the sunglasses lenses should provide good contrast. Finally, the most important is that sunglasses for sailing should have 100% UV protection.