Ripl

I personally always use Dark Sky, but here's ones I know about from friends, colleagues and blogs I have read. Can't wait to see what other people like to use!   

• C-MAP https://www.c-map.com/app/ 

Boat Brand Apps: 

• If you own a Sea Ray: https://www.searay.com/us/en/sea-ray-plus1.html 
• If you own a Boston Whaler: https://www.bostonwhaler.com/marketing/mywhaler-app.html 

Also, here's an article on Discover Boating with some good ones: https://www.discoverboating.com/resources/marine-navigation-apps