In most of the cases, one handhold a marine binocular on boats at sea that is seldom quiet.  So, the maximum power for handheld marine binoculars is 7x.

At night in the sea, without the tradeoff of handholdabilty, a marine binocular with as much light grasp as possible is needed.  So far, 50mm is both handholdable and has the light gathering power needed.

So, it's no wonder that almost all the marine binoculars are 7x50. 

For marine use, the binoculars should have good wateproof performance.  And, for professional mariners, the built-in illuminated commpass and range-finding reticle is a plus.

Our 25/40x100 standard and 25/40x100 painted are good for baywatchinng and can be set up on the coastline sites like towers or life guarding posts.

The binoculars below are ranked by suitability for marine with 1-5 stars:

5 star: 7x50 compass FL, 7x50 compass MS LW, 7x50 MS, 7x50 FB, 7x50 HG
3 star: 8x40 FB, 10x50 FB,10x50 MS
2 star: 25/40x100 standard, 25/40x100 painted

Besides suitability,you should probably consider the cost performance of each model using the cost performance formula.