I have probably spent between 15 and 20 nights sleeping on a boat, so far in my lifetime. The worst night's sleep I ever had on a boat was when my husband bought a 25 foot yacht that slept 5 people. We were a family of five, which included our youngest, then two years old. Without a restraint for him, I found it impossible to sleep on the boat, since it was too warm to sleep without both the galley door and the hatch open to allow for cross breeze. The slightest sound and I was awake....I was terrified that I might wake up and find him gone :)