Plastic trim between tile and concrete coming off - what is a safe glue?

I have a black plastic trim piece (sort of like a deflector?) that goes around the pool just above the water line between the tile and the concrete top edge. In one area it started coming loose, it looks like it was put into the concrete when it was made, but I'm wondering if I could glue it back together before it completely comes off. Is there any specialty glue that's safe for the water?