I can tell you from extensive experience that there is absolutely nothing like sleeping on a ship, especially in a small, coffin-like bunk in a room with no win

I can tell you from extensive experience that there is absolutely nothing like sleeping on a ship, especially in a small, coffin-like bunk in a room with no windows: the gentle rocking, the absolute darkness, and the white noise combine for incredibly deep and restful sleep. The shitty, thin mattress caused me long-term back and shoulder problems after sleeping on it for months on end, but with all of the other advantages I still slept well every night.