I've had the Blackwater 12.5 for over two years. In that time I've paddled numerous calm rivers and lakes. The fun starts when you get comfortable enough with the boat to take it into the surf. My first time out was rough, but coming from my stubby little intro boats, the 12.5 was far easier to control. By my second trip out I'd learned to roll it 2 out of 3 times. Expect to get plenty wet in rough water. After getting comfortable in the chop, I now routinely take it out in rough swells. The boat will handle reasonably well in anything less that 6 feet and I'm considering trying it in worse. Last March I took the boat out on Galveston Bay with 4'-5' swell, high wind and intermittent showers. I paddled out to Redfish Island (roughly two miles) and never even tipped over the bait bucket which was balanced on the rear hatch.
The boat will do whatever you want it too. It's built like a tractor and laughs at rocks and oyster beds. The 12.5 is not the best choice for multi-day trips on open ocean, but has served me quite well on four-day trips downriver. I would feel comfortable in this boat for longer trips on open water, but the group will most likely have to slow down for you. While the wind is not too hard to overcome, ocean currents can turn paddling into more of a chore than you're buddies with directional rudders have to deal with. I bought the boat because when I want to get on the water, I don't want to deal with a 17' plus monster, want to worry about a rock ending the life of a $2,000 boat, and I want to feel confident alone and a long way from home. The Blackwater has served me well. The sexier boats catch my eye regularly, but I've never felt at a loss out on the water.