Ok, I thought of another one!
I got a tank off CL
that came with lights and a canister filter and stuff. A lot of the equipment was fairly new and still have the packages and instructions and whatnot. Well. the canister did not. I had to google how to set it up. When I started it, it wouldn't pump water, so I looked online for help and I was told to suck on the outflow tube and pull water into the canister to get started. There are little flow control switches, so that seemed like no big deal. Well, The filter was underneath the stand already so I had to kind get down under the stand too and I couldn't see super well, because it is dark under a fish tank stand. I chose the in-take tube, and I got a mouth FULL of water as well as spraying it all over torso and face and the floor around me. It was not my proudest moment. Lol.