I recently became aware of a really interesting game called Rule The Waves through this review:
http://www.wargamer.com/reviews/review-rule-the-waves/Essentially, this is a sand-box like game where you play a semi-historical campaign and have to design all your own ships from the keel up. Now, this game is pretty basic when it comes to graphics, but it looks really engrossing...I see myself losing hours and hours of my life to it! It's moved to the top of my game purchase list, actually.
