A clock on the bridge. Seriously, where are the clocks? They never show time on the view screen, and you don't see people pulling out communicators to check the time. There have been a couple of Starfleet officers shown wearing wristwatches over the years, but not often. I have never heard ships bells, either. So how do they know what time it is?
because engineering is a room probably filled with all kinds of pipes and fluids and coolants and water, and anything can happen, therefore anything critical should be built with that in mind.
your laptop might not be waterproof, but the controls in the engineering room of a modern ship or spaceship will be. And even an iphone is fairly water resistant now.