Thanks, guys!!! Shooting something like this and finding out that other people appreciate what I saw encourages me more than you can imagine. I appreciate the suggestions, too.
I did use a tripod, which is the only way I could get this one at all. By the time I saw this, there was very little light left. I started to switch lenses, but didn't even think I had time for that. I even tried to paint it a bit with a flashlight, to keep some detail in the boat.
I was worried about the softness of the tree line at the time, and tried to use a smaller aperture. I shot one at f/16, right after this. The only issue there was that the waves (they're there, just smoothed out by the shutter speed) had the boat moving so much that the ONLY thing in focus was the trees and sky. If I'd seen it earlier, I would have had time to play more, but there just wasn't enought time, then.
I also could have increased the ISO, now that I think about it. I'm still having to get used to that ability. Sometimes it's right there (as an option) and sometimes I revert to my film days, when it was just "find the shutter speed and get an aperture that works". I've got a lot of learning curve to go!!!
The funny thing is that the original boater I tried to shoot started passing back and forth through the scene during these longer exposures. By that time he was a silhouette, in my eyes, and nothing more than a smudge on the file.