7. The beautiful blue balloon on the sand
It looks like a child’s lost party balloon: translucent blue-violet, glossy, the size of your palm, lying on the wet sand. It’s a Portuguese man-o’-war, and the tentacles trailing invisibly meters across the sand sting ferociously for days after the animal is dead — beached ones injure more people than swimming ones, mostly children who pick them up and adults who nudge them barefoot. One on the sand means more in the water (they drift in flotillas on the wind). The protocol: look, photograph, tell the lifeguard, touch nothing — and check the purple flag, because this is exactly what it flies for.
8. Brown, churning water near a river mouth or after rain
That tea-colored water where the river meets the beach isn’t just ugly — it’s the most statistically loaded water on the coast. River mouths combine outflowing currents that work like conveyor belts, sudden depth changes, debris you can’t see, runoff bacteria after storms — and, on coasts where it’s relevant, they’re where predators feed, because that’s where the murk and the baitfish are. Lifeguards’ plain rule: don’t swim at river mouths, and skip the ocean for 72 hours after heavy rain — the runoff alone (the bacterial kind) sends more swimmers to the doctor than anything with teeth ever will.