Seen a glowing beach?

i was on a beach with friends in wales, UK once. We were going cliff climbing at night. And we noticed that we were leaving blue glowing footprints. as we got further onto the beach there was more blue glowing. like millions of little blue dots everywhere. We were gobsmacked, we found this pool of water that was glowing like it had mood lights in it. we then chucked a rock in and it shimmered with colour between blue and purple and green, like a computer visualization. It was amazinb, we were gobsmacked and didnt know wot the hell it was. we then freaked out because we thought it could radio active waste. so we scuttled off the beach. later that week we found out it was phenomenon that happens hardly ever, like once in every 1000 years for each beach. where certain deep sea algae/plankton (cant remember which) comes to the shore and reacts with the air and light and starts glowing blue.