Back in the eighties (yes I am that old) I was in the back seat of a BO105D. The drivers up front were doing a line check and I was along for the ride to observe a Decca Navigator snag (yes, really, I am that old). We were flying to an exploration rig which had opened the deck especially for us (this was a Sunday). As I thank you, we were carry the Sunday papers out to them.
When we landed on, the pilot asked me to supervise the unloading and to grab the nav bag out of the back, which I duly did.
Once strapped in again, he asked me to find the Aberdeen area chart. Head down in the back, we lifted off the deck and as we started to move forward, I heard an engine wind down. I looked up to be faced with the surface of the sea where therer should have been horizon. After the first shot of adrenaline, I noticed a hand on one of the throttles. The bastards had briefed while I was outside and didn't deem it necessary to mention the fact to the engineer once he returned. I am sure the CVR had a few choice words on it that day.