This post includes saltwater fishing-related things to do that can be done during the winter months.
Clean, inspect, and store fishing tackle.
Service rods and reels.
Winterize boats, trailers, batteries, and other equipment.
Check safety equipment for damage, wear, etc. Where applicable, remove and store batteries.
Perform software and firmware updates on electronics. Download and update smartphone apps.
Renew fishing licenses, HMS permit, boat ramp access permits, boat and trailer registrations, EPIRB registrations, FCC licenses.
Take a USCG Auxiliary course on safe boating, basic navigation, or other topic.
Make a list of tackle, electronics, batteries, and other equipment that needs replacing.
Organize, edit, and print fishing photos.
Visit a bookstore and stock up on fishing books.
Attend fishing seminars, outdoor expos, fishing shows, and other events.
Do fishing research, including tips and techniques, locations, bait, tackle, weather, navigation, and other subjects.
Cook frozen fish.