A good set of binoculars is considered by most experienced skippers to be essential boat gear. And, many will ensure they have two sets aboard, often with different characteristics for different purposes.
There are a range of features that define a set of binoculars and affect efficiency and usefulness in the maritime environment. First will be the set’s rating in terms of magnification and field of view. It is commonly accepted that 7 x 50 is the right rating on the water. The 7 stands for the magnification or 7 times magnified. The 50 stands for the diameter of the front lenses and this width combines a wide field of view with better than average light gathering for use in low light situations.
But there is more to consider when selecting a new set for your boat. BoatUS offers an excellent survey of things to consider on their blog.
Read more here.