When you see another boat raising and lowering their arms repetitively what is the first thing to do?

If you see another boat raising and lowering their arms repetitively, the first thing to do is to determine if they are signaling or trying to communicate. This could indicate they need assistance or are giving instructions. It's essential to approach with caution and assess the situation, ensuring your own safety and that of others. If necessary, signal back or approach to offer help.