Between "beach" and "swimming pool", the island keeps a third category the brochures undersell: charcos — natural sea-pools in the lava, refilled by every tide. The friendliest live in Punta Mujeres, a whitewashed fishing village that is basically built around its pools: ladders, little platforms, grannies doing their daily lengths at nine sharp. The wildest are Los Charcones, below Montaña Bermeja near Playa Blanca — a chain of impossibly turquoise basins carved into dark lava cliffs, gorgeous and genuinely dangerous in swell. The rules of the charco are universal: go at low-to-mid tide, calm sea only, never turn your back on the ocean, and watch where locals swim. Master the timetable (the tides card) and you unlock a dozen of the island's best swims — most of them free of both sand and crowds.
The lava coast looks hostile to swimmers until you learn to read it: everywhere the flows met the ocean, they left pockets, arches and basins that the tides fill twice daily with clean, renewed seawater. Islanders have used these charcos as their neighbourhood pools forever — some improved with a ladder and a handrail, some left exactly as the volcano poured them. They're the most local aquatic experience the island offers: no entry fee, no music, plenty of unwritten rules.
Punta Mujeres is the capital of the domesticated charco. The village north of Arrieta strings its houses along a low lava shore threaded with pools — the biggest by the centre with steps and ladders, smaller ones tucked between houses like private baths that happen to belong to everyone. The scene is the point: kids leaping at high tide, the morning swimmers' club at their fixed hour, neighbours watering geraniums between dips. Water is glass-clear, refreshed by every tide, with enough small fish to justify a mask. Etiquette: this is a living village, not an attraction — park properly, keep voices down, buy your lunch locally (the fish here is serious). Nearby, Punta de la Vieja and the pools around Arrieta extend the collection.
Los Charcones are the other end of the spectrum: wild, unguarded, and on the right day the most beautiful swimming spot on the island. On the raw west side of the Playa Blanca peninsula, reached by a dusty track and a scramble, the ocean has carved a series of basins into low dark cliffs — turquoise bowls connected by channels, deep enough to swim properly, framed like infinity pools with the Atlantic exploding just beyond the rim. That framing is the warning: this coast takes the full west swell, and rogue sets wash over the rims with force. The protocol is absolute — calm-sea days only, low-to-mid tide, never alone, never on the outer rims, and if spray is crossing the pools, it's a photo stop, not a swim. People have needed rescuing here for ignoring exactly this paragraph.
Honourable mentions for your collection: the Charco del Palo pools on the naturist coast (swimwear optional territory — the village is one of Europe's oldest naturist enclaves, mentioned matter-of-factly, as the island does); the calmer lagoons of Caletón Blanco (card 76); and Punta Mujeres' cousins in every fishing village north of Arrecife. The general theory is always the same and always worth repeating: the tide is the timetable, the locals are the lifeguards' union, and a charco that's empty at golden hour usually isn't undiscovered — it's closed by swell, and the villagers all know it. Swim where the grannies swim. They have a perfect safety record.