You might also have heard these marketed as "blue blocker" lenses. The theory behind masks with a "contrast" lens coating is the yellow tint blocks the blue color (be aware that this not adjusting the color, it is reducing the amount of total light) which because of how the retina in the human eye functions allows better perception of edges and movement via the remaining light. For divers, the application was primarily for spearfishing, i.e. hunting. Most experts, including the American Academy of Ophthalmology, do not recommend the feature as they likely "do not really work" for their advertised purpose.