The game actually came in card packs. It was a "constructible strategy game."
When you opened up a pack, you got cards made from styrene. One each styrene card were parts of one ship (larger ships were spread out over a couple of cards or three). Rather detailed artwork were on both sides of the card. What you did was to punch out the pieces and then construct your ship. Here's a pic from the Vikings expansion, Pirates of the Frozen North:
What was annoying was that beyond the starter pack, the expansion packs were blind buys. There was no way to figure out what kind of ship you were going to get in the pack, which made fleet building a bit of a pain unless you had a friend that was also building a similar fleet and you could trade. I used to frequent the communities and trade with the members there for ships that I did not have for ships that I had too much of.
Also included in the pack were a rule sheet and a pair of really, really small dice, about 5mm on a side.
One of the cards was a range finder/ruler that you could use to measure distance.
As for what you did--fleet or ship-to-ship battles depending on the points. Facing and turning rates really mattered since you could do things like broadsides. The modular nature of the models meant that if my ship took damage, I could actually removed bits off ships (sails for example). More often than not, I just used the fire/smoke damage counters (notched so that you could tack them onto the damaged sails or weapon).
It was a rather fun game. Please note the past tense. WizKids the company that made it was shut down by Topps a few years ago and with it the game went. The communities are still out there, though a Google search may be difficult. You can find more information if you use "pocketmodels" or "constructible strategy game" as search terms. As for where to buy the game? I'm lucky that I know of three shops on my island that stocked them and after all this time, there are two that still have stock (they occasionally ask if I want more packs). If your store did not stock them in the card section, your best bet would be eBay or Amazon.