Yes, and no.
I played Man O' War many ages ago and it was ok; Uncharted seas is much faster paced and (IMO) much more fun.
The ships are nicer too (again, just my opinion).
It is from Spartan Games ( http://www.spartangames.co.uk ).
I know that yottaquest stocks some Uncharted Seas stuff and that there are at least a couple people around here with fleets (not counting me and my two buddies that just got started).