What immediate action should you take when operating a bow if you hear the fog signal of another boat you cannot see?

If you hear the fog signal of another boat while operating a bow, you should immediately reduce your speed and sound a warning signal, such as a horn or whistle, to alert the other vessel of your presence. Additionally, maintain a lookout for any signs of the other boat and be prepared to take evasive action if necessary. It's essential to navigate cautiously and keep your course steady to avoid collisions.