Ships can communicate via flags, and one of the ways the flags can be used where each flag represents a letter from the alphabet. If the hunters are unlikely to recognise the flags then a decoding sheet could be given in a previous clue. The example below says “Under the stairs”:
![Shipping flags spelling Under the Stairs](https://www.treasure-hunt-ideas.co.uk/wp-content/uploads/2023/12/flag-signals.png)