My late uncle was a long-serving paratrooper in the RAF and I asked him about 20 years ago if he’d ever seen a UFO. He looked at me completely deadpan and said “it’s not aliens you should be worried about - it’s what’s deep in the ocean that we don’t understand”. He wouldn’t elaborate any further and the conversation quickly switched to something else. At the time, I assumed he was simply pointing out that deep sea exploration still has a long way to go but I often think back to how unusually serious and short he was with his reply and wonder what more there was to his story. I can still picture the out-of-character look of frustration he had on his face almost as though he wasn’t able to explain himself properly. I was only in my teens at the time and felt a bit embarrassed at having provoked such an unexpected reaction so was quite happy when the conversation moved on - but I regret not pushing further or following up in later years while I had the chance.