No not the friendships, the Liberty Belle. I know at DLR you could not ask to captain. The "secret" question was to ask a CM "how's the view from up,there." We had to wait for the next trip but it was a lot of fun doing it!
I did this in California last year. No secret question, I just asked the CM at the boarding. I had to wait until next rotation as someone else had already asked.
When the boat came back I was escorted onboard before all the passengers and brought up to the captains area. It is great fun, and you get a certificate afterwards