A friend was a board director of British Airways. I asked him if he could give me a letter to show at the airport check-in, telling his staff to look after me and to waive excess-baggage charges. He said it was more than his job was worth to do that, and that I’d do better to make friends with someone who worked at the airline’s check-in desk.
That encapsulates the problem of travelling with dive and underwater photography equipment. It’s a totally hit-and-miss system unless you are prepared to pay up. You take your chances and hope the check-in staff will be lenient …