I came across a hire boat from Anglo Welsh on the Llangollen a couple of weeks ago who decided it was a grand idea to open every paddle they could find - all at the same time. I suggested they might just want to open the bottom paddles as they were hoping to descend, an idea echoed by an employee of a different marina who was returning a boat.
The "crew" of the offending boat got quite annoyed, saying "I know" repeatedly - a bit odd since they evidently didn't know. Thankfully I was going in the opposite direction so they didn't cause me any further problems.
They had been instructed on the use of locks by Anglo Welsh, but that had been the previous day and they had obviously got short term memory problems, or simply didn't bother listening.
A few years previously I came across a stag party, 10am and two blokes were starting to open all paddles. It transpired they were the two most sober of the party, they were not the ones who had been instructed in lock operation, and I spent half an hour running them through the procedure. Again they were going in the opposite direction to me!