Sea sun and computer

We were leaving for a two week sailing holiday in the British Virgin Islands. We parked in the long term car park at Gatwick and took the airport bus to the terminal. As I left the bus I noticed that someone had left their laptop behind on a seat. I picked it up and handed it in to lost property. I didn't think any more about it other than the glow of righteousness. We proceeded from Gatwick to Antigua and on from there on an island hopper to Tortola . When we arrived in Tortola we proceeded by taxi to Sopers Hole to pick up the yacht "Gunshot" which we eventually found moored in a raft of boats. We opened her up and unloaded and switched on the electrics. We found all was well apart from the 12v dc feed for the navigation computer that we'd brought with us. We traced this to a fuse but couldn't find a spare. It didn't really matter because we were not due to leave until the morning. We noticed by this time that the boat moored next door to us was occupied, faffing around getting their bearings just as we were. We struck up a conversation, shared a glass of wine, and, conversationally, asked if he had any idea about fuses and power supplies. He suggested plugging in his computer to double check our diagnosis. He said he was lucky to be able to do so because he had left his computer on the bus at the airport, but someone had kindly handed it in. "T'was I!" I happily told him...........it was a good evening we had.....................