Final answer:
The first thing you should do when encountering another sailing vessel is to take actions to avoid a collision by following right-of-way rules and giving way to the vessel on your starboard side.
Step-by-step explanation:
The first thing you should do when operating a sailing vessel and you encounter another sailing vessel is to take the necessary actions to avoid a collision. This can be done by following the right-of-way rules and giving way to the vessel on your starboard side. If both vessels have wind coming from the same side, the vessel that is windward (upwind) has the right of way.
For example, if your vessel has wind coming from the right side and the other vessel has wind coming from the left side, the other vessel has the right of way. In this case, you should alter your course to allow the other vessel to pass on your starboard side.
It's important to communicate with the other vessel using sound signals or VHF radio to ensure both vessels are aware of each other's intentions and can maneuver safely. Always maintain a safe distance and approach the situation with caution.