Tenerife's natural pools: seven places to swim in the Atlantic

In 1706 lava from the Trevejo volcano poured down into Garachico, buried the harbour and froze into jagged shapes where it met the sea. The ocean has filled the gaps ever since, and on a calm day the water between the black rocks lies still while the surf breaks white on the outer edge. Some of the pools are shallower and calmer, and those suit young children. The lava is sharp: wear water shoes. The pools close when the swell is heavy, but even then it's worth stopping to watch the waves pour through the channels. Come early, as it gets very crowded.

The sea itself carved this basin out of dark rock, about 40 steps down from the road. On a calm day you float in clear water with the waves booming beyond the rim; on a rough one the pool turns to white water and all you can do is watch. A green, yellow or red signal shows the day's conditions. Swim only on green, because big waves set up currents strong enough to pull you out to sea. There are no facilities at all: no toilets, no shade, just rock, the sea and the cliffs of the north coast.

Pools held inside a reef of dark lava, with water so clear you can see fish from the surface. Bring a mask and snorkel for a closer look. The drive down from La Guancha runs through banana plantations to a car park with room for 15 to 20 cars. The last stretch of road is narrow, with few places to pass, and you may have to reverse. From the car park it's a few minutes over rough rock to the water, so wear water shoes. César Manrique, the Lanzarote artist, singled out this pool for praise on his 1986 visit to La Guancha.

Two huge ocean-water pools, a calm lagoon behind a breakwater with a small black-sand beach, and a separate children's pool make Bajamar a good choice for families. Swimming is free, and there are changing rooms, showers, toilets and a kiosk. Steep green slopes rise behind the town, there are no big hotels on the front, and the crowd is relaxed and mostly local. Stay on for the sunset over the sea. On days of heavy swell, waves break over the outer walls.

A pool built on the shore, where every so often a wave clears the wall and the Atlantic pours straight in. At low tide the water is calm enough for a gentle float or steady lengths. At high tide the waves come over hard enough to push you around, and the pool is for strong swimmers only. A rail runs round the edge, and the fountain in the middle has a ledge to sit on. Bring goggles: small fish come in with the waves. Behind the village rise the ridges of the Anaga mountains.

César Manrique's seawater complex on the seafront of Puerto de la Cruz: pools and a lake of 15,000 square metres, with islands of volcanic rock, footbridges and grottoes to swim around. You get salt water without the waves, so this is the place to go when the swell makes the sea along this coast too rough for swimming. Entry is by ticket, with a sun lounger included, and there are bars, a restaurant and children's areas. Pick a sunny day. Everything is open-air, and on a grey morning the seawater feels cold.

A seawater pool on the promenade at Alcalá, looking across the water to La Gomera, with La Palma on the horizon when the air is clear. Put on a mask and you may see fish and even octopus. The pool is at its best at high tide, when fresh seawater washes in, so check the tide table before you go. It's sometimes drained or closed without notice. There are no shops at the pool itself: bring food and water. Public toilets are about 120 metres away.