What was your first newbie moment?

Went for a week using the shower house and heating dish water on the stove, waiting for a warranty appointment for a water heater that didn't seem to be working right, while on our second voyage. Then I found that the kids used the outside shower to wash the dog, and didn't turn off the knobs and only turned off the flow control. The cold water was bypassing the heater and going straight into the hot side of the system through the shower faucet.