Pirate_Wench here;
Haven't read all the replies, but have to scream, YOU DO NOT HAVE TO BE UNDER 26 TO GO TO A MARITIME ACADEMY. The only one that requires that is the "Merchant Marine Academy" aka "Kings Point", which is a military academy like West Point, and requires the congressional letter, blah blah blah. It is far from the only option. I went to the California Maritime Academy, part of the CSU system. You can be ANY AGE and go to this school. It is 4 years, with the possibility of finishing in 3, it is not cheap, and you have to wear uniforms and half act like you are in the military (you are not). I have a bachelor's degree from this. There is also the Great Lakes Academy, Maine Maritime, Mass Maritime, a Maritime branch of Texas A&M, and SUNY maritime in New York. Some academies are tougher on the quasi-military aspects than others. All make you a Merchant Marine Officer, deck or engine, and give you a degree. There are a ton of people doing this as a second career.
Also, it took me about 7 years to move up enough in my union to feel confident in getting that much work/year at that higher contract level. Now I can work a lot more, but I don't want to. I once went over a year without getting a shipping job, and I've worked much lower paying contracts. My yearly income has been as low as $45K and as high as $90K. Talk about having to think about money differently! It is a strange business, I can assure you :)
p.s. You can work your way up without going to college. I wouldn't recommend this method. Those guys are at sea for upwards of 7-8 months a year!