I don't think we slept another minute that night. Every few minutes one of us would groan or be like, "I can't believe this is happening for real" or, "Do you think this is a thunderstorm?" but there was definitely no sleeping. To add to the ambiance, you could hear someone throwing up across the hall.
In the morning, we asked the two couples who had been on the boat for three days before us if the last night had been a crazy thunderstorm or something. "That was the calmest night we've had so far," they said. At first, I thought they were joking - how could that have possibly been considered a good night?? But it turns out they were being completely honest. And each night was just as bad. But we started taking mareol, a dramamine equivalent, before we went to bed each night. We still didn't sleep through the rocking, but at least we weren't nauseated from it. We also only sailed for a few hours each night, so we would go to bed really early and get in a few hours of sleep before we set sail and started our roller coaster ride.
Jenna got sick the day after I did (we were quite the popular pair on the boat, let me tell you), and after we were both "better," we basically just had a low but constant level of sea-sickness plus an inability to keep any food inside of us for the rest of the trip. Definitely unpleasant, but more manageable than when we started.