9. Foam, seaweed or debris moving OUT to sea in a line
Here’s a sign hiding in plain sight: watch what floats. Waves push everything — foam, kelp, that escaped beach ball — toward the shore. So when you spot a line of foam or debris traveling steadily away from the beach, cutting out through the surf like it has an appointment, you’re looking at water leaving the beach in a hurry — a current strong enough to carry whatever floats, including swimmers. Lifeguards literally use this to spot trouble from the tower. It connects directly to our mystery entry from page 3 — and we’re two pages from naming it.
10. Square-flag and double-flag systems most visitors misread
Quick world tour, because flag illiteracy hurts tourists most: red-over-red (two stacked red flags) = water closed, full stop. Red-and-yellow halved flags = lifeguarded swimming zone — swim BETWEEN them, not wherever looks nice. Black-and-white quartered = surfboard zone, no swimmers. Yellow = caution, weak swimmers stay shallow. Green, on beaches that use it = calm conditions (and famously, the most dangerous flag of all — because it switches brains off). And no flag at all on an unfamiliar beach doesn’t mean safe; it usually means nobody is watching. Thirty seconds reading the flagpole beats a very bad afternoon.