While learning about day shapes, I have really come to realise that sometimes you have to make your best guess.

When I look at this picture, it reminds me that people get things wrong. I took this picture as I thought that I could use it in our lights and shapes quiz, it was only when I started compiling the quiz that I realised that this shape does not exist, so you simply have to make your best guess.

To make your best guess, you use other information that you can see, how is the boat moving, is there any other information that you can see. For example in this picture there is a diver down flag flying that has clearly seen better days, and if the two arrows were pointing outwards rather than inwards, then the shape would mean restricted manoeuvrability, so this was probably the intention.