Ocean rowing, though incredibly challenging, is not difficult to get into if you have the time and the money to undergo intensive training.  It is of course recommended that you have an interest in rowing before you make the decision to take up the more physically and mentally intensive version of the sport, and of course it does help if you have prior rowing experience.  The main thing to remember is that ocean rowing demands incredible strength from it's sports-people and can be as much about mental challenges as it is about the physical.

The first thing to undertake if you are considering >ocean rowing as a pursuit is to find your nearest safe body of water and start rowing.  It doesn't matter if you're not in immediate proximity to an ocean or sea (although this does help); so long as you can get experience out on the water and in all manner of conditions.  Try to clock up time in wet weather as well as dry, and also try to gain experience in windy conditions (within reason).  Winds and strong waves are amongst the most difficult challenges the ocean-rower faces, so it is important that you ready yourself for these possibilities.