My husband and I take our boat out fishing or to watch cetaceans for forty +/- weekends during the year. That's a whole lot of cold turkey sandwiches! I am so sick of turkey, I've just about given up on eating while on the boat leading to some unpleasantly lightheaded afternoons.
We have tried soup in the thermos a few times. Not so easy when the boat is pitching about, but still awfully nice when it's cold out. Fruit works well, too. When you're out the door at 4am and don't return home again until sometime after 7pm, it's important to have some good fuel to keep a person going.
We're trying to stick with healthier, convenient-on-the-boat food that tastes good cold. We don't mind having to use a spoon or fork, can precut anything at home before taking off. I do like tuna sandwiches, but for some reason, they are hard to get down when I'm catching fish (can't eat sushi the same day I fish either, go figure). Any new ideas would be a wonderful break from the same old, same old.