My partner (35M) and I (21M) are on holiday in Spain at the moment, and very much enjoy snorkeling in the crystal clear waters. We went to a remote beach which has no lifeguard and is not very touristy , as the beaches where we were staying were packed and too hard to see the water. We were swimming along the rocky coast, and the water gets quite deep quite fast, but there's very little current and it's in a bit of an alcove so it's safe for majority of swimmers. However when we were swimming we spotted, a few metres out, a giant jellyfish. We swam away from it, but then I passed a family who were English and were swimming that way with two young kids (maybe about 5 or 6?). I stopped and said to the dad that there was a jellyfish a few metres out that way, but if they stay by the rocks they would be okay. I said just be wary as it was fairly large and also because there is no lifeguard (so no medical supplies). The kids were also still using floaties so naturally not the best swimmers. They thanked me and I swam past. It's noted that the parents didn't have any goggles. Then, about five minutes later the girls were screaming about jellyfish, and I heard the parents exasperatedly say there was no jellyfish and to keep swimming. This is where the issue started. The parents would not stop whispering and glaring at me, and one of them commented I intentionally scared their children. My partner says I should've kept myself to myself and not said anything. The girls wouldn't stop saying about jellyfish and they had to get out eventually, but before they did they were saying they saw jellyfish and the parents were telling them there was none, and the father was trying to coax the daughter to him. But about two foot away from him were two jellyfish. The daughters refused, and I saw them get out, and the parents are still giving me death glares from across the beach, supposedly for ruining their beach day. I don't have kids so I can see how that was frustrating, but I didn't want them to get hurt...AITA? Tldr: I warned a family with young kids about the jellyfish in the water, and scared the children until they had to get out.