Can't tell if this is some kind of bait or not, but besides fishing and the Navy/CG, there is the merchant marine. Depending on the company and ship you can be out at sea as long as several months or for something like tugs, be home for dinner every day.
Pay is pretty good especially when you are an officer in a union.
Entry requires you to either go to a maritime academy for four years or to be unlicensed you can go to trade school. Not much upward mobility beyond being the captain/chief engineer which you can accomplish within a decade.
Main jobs on a ship include the engine department (making sure engines, pumps, shitters, electrical, etc are working), deck department (navigation, ship handling, painting/chipping, ship restoration, safety equipment inspection) and on bigger ships stewards department (cooks/bakers/waiters etc).
You can work oil tankers (very monotonous, but also very stable, can be stuck sitting outside port until prices become favorable), container ships (see above but more strictly adhering to a schedule), cruise ships (shit pay but imagine all the strange you get in your dress whites), tugs (hard work and long hours but some of the most interesting and varied work on the sea, OSVs (industrial water taxis), oil rigs (where the real money is at), and a whole host of other ship types.
If you still want a military element there is military sealift command for the USA which are the civilian mariners who resupply Navy vessels at sea.
All in all, usually once you are off the boat you can do whatever the hell you want innawoods as long as it's not weed because they test for that.
Also abandon the ideas of exploring foreign ports because modern merchant vessels can all be unloaded and loaded in less than 24hrs.
Shipyard will probably give you the most time ashore and that's usually in Louisiana which sucks.
