El Puertito, a small cove south of Adeje. You wade into the water up to your waist and 3 meters away, an 80 cm green sea turtle grazes on 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 shore snorkeling delivers on its promises. The water is clear (15-25 meters visibility), warm (20-24°C), and marine life is there, within fin's reach.
El Puertito (Adeje) is the most famous spot: resident green sea turtles, calm water in the cove, depth 2-5 meters, parrotfish, octopuses in crevices. The problem: crowds. Arrive before 9:30 am or late afternoon. Abades is an abandoned former military village on the east coast — easy access via a dirt path, varied rocky seabeds, octopuses, juvenile barracudas, and almost nobody. Radazul is a local favorite: a municipal pier, stingrays resting on the sand at 5 meters depth, squid at night for divers. Los Abrigos: a quiet fishing port, cuttlefish under boat hulls, and the best visibility on the south coast. La Caleta (north of Adeje) is the discrete spot: trumpetfish, moray eels in the rocks, and a small beach restaurant for lunch.
About a dozen PADI and SSI centers on the south coast, all reputable. A beginner dive (Discover Scuba Diving) costs €50-70 and takes place in open water, not a pool — you see things on your first dive. Main sites: Las Galletas (rays, sea turtles, 12-18 m), Alcalá (caves and tunnels, 15-25 m), Los Gigantes (dramatic underwater wall, 20-40 m, angel sharks in winter). Radazul is the favorite playground for local divers: shore access, 20 m+ visibility, abundant marine life, legendary night diving (squid, hunting octopuses, mobile rays). The water never drops below 19°C — a 5 mm wetsuit is enough in winter, a 3 mm in summer.