On Plenty of Fish, “watching” someone means that you have expressed interest in their profile and added them to your “Watched” list. This allows you to receive notifications when they come online, update their profile, or send you a message. Watching someone does not mean that you have sent them a message or that they are aware of your interest.
Watching someone on Plenty of Fish can be a way to show interest in them without being too forward. It can also be a way to keep track of someone you’re interested in without having to message them directly. If you’re not sure whether or not to send someone a message, watching them can be a good way to test the waters and see if they’re interested in you.