The #1 rule for being at sea is pretty simple:
If you don't want it to break or hit you in the head, tie it down.
As I've said before, being out at sea is sort of like experiencing a two-week long earthquake. And you plan accordingly. (For those of you who have experienced actual earthquakes before, I should say that it's like two weeks of s-waves, no p-waves at all.)
The ship is built for it: drawers in the staterooms all have secure latches, the armchairs in the staterooms are strapped to the wall, and the doors all have magnetic catches to keep them from swinging back and forth if you don't close them properly.
In the science lab, everything large gets strapped down. Everything.
Of course, not everything is big enough to secure with a ratchet strap. But there are other ways of holding those things down.
Trying to do science while everything is rocking back and forth makes for an interesting ride.