Search Results: staring at girls chests

I was on vacation with my boyfriend at the beach when I noticed that a guy, lying beside his girlfriend, stared at me a lot. I didn't think much of it at first since everyone look at people. But then he shifted away from the girl, layed on his stomach with his head away from his girlfriend and towards me, staring while I put on sunscreen on my chest. It felt really weird since he didn't take his eyes off of me. I mentioned this to my boyfriend because he could sense that I was uncomfortable and he started to stare back at the guy angrily. My boyfriend gets really jealous when I get (always unwanted) attention from other guys.

Later when neither my boyfriend nor his girlfriend were around he asked me if I needed help to put on sunscreen. I obviously said no.
My boyfriend had seen him walking up to me and asked me what he had wanted. By then the couple had left so I told him and he walked away without saying a word to me. When he came back a couple of minutes later he asked what I had told him and in which way I had said no. Later in the hotelroom he brought up stuff from the past (guys that I saw as friends who had taken interest in me while we were in a relationship).
He told me "if they're at the beach tomorrow I want us to lie as far away from him as possible". He's been so overprotective in the past that I'm not entirely sure what's normal anymore. How would you react if this happened?