El Puertito, small cove south of Adeje. You enter the water up to your waist and 3 meters from you, an 80 cm green turtle grazes on the algae on the rocks. No need for a boat, no need for a bottle, no need for a wetsuit in summer, a mask and snorkel are enough. Tenerife is one of the rare places in Europe where onboard snorkeling keeps its promises. The water is clear (15-30 meters of visibility depending on conditions), warm (20-24°C), and underwater life is there, within reach.
El Puertito (Adeje) is the most famous spot: resident green turtles, calm water in the cove, depth 2-5 meters, parrot fish, octopuses in the crevices. Problem: the world. Arrive before 9:30 a.m. or late afternoon. Abades is an abandoned former military village on the east coast, easy access via a dirt road, varied rocky bottoms, octopuses, juvenile barracudas, and almost no people. Radazul is the locals' favorite: a municipal pontoon, stingrays resting on the sand at a depth of 5 meters, squid at night for divers. Los Abrigos: a quiet fishing port, cuttlefish under the hulls of the boats, good visibility (variable depending on the day). La Caleta (north of Adeje) is the discreet spot: trumpet fish, moray eels in the rocks, and a chiringuito on the beach for lunch.
Around ten PADI and SSI centers on the south coast, all serious. The baptism (Discover Scuba Diving) costs 80-120€ depending on the center and is done in the open sea, not in a swimming pool, you see things from the first dive. Main sites: Las Galletas (rays, turtles, 12-18 m), Alcalá (caves and tunnels, 15-25 m), Los Gigantes (dizzying underwater wall, 20-40 m, angel sharks in winter). Radazul is the favorite playground of local divers: access from the shore, visibility 20 m+, abundant wildlife, legendary night diving (squid, hunting octopuses, moving rays). The water rarely drops below 18-19°C in winter — 5 mm is recommended from October to April, 3 mm is sufficient in summer.