Arcanzil

The rock at Arcanzil sits with its base at about 15 metres and rises close to the surface, rarely fully covered even at high water. Zodiacs drop divers a short run south of Sesimbra, near Cabo Espichel, directly onto the formation. From the base, the seabed keeps sloping down to the south and east, reaching about 22 metres before it flattens into sand, while the rock's western side is broken by crevices and raised stones down to roughly 10 to 12 metres. Nudibranchs and octopus turn up in both of the dive's independent accounts, including mating nudibranchs spotted on one visit; scorpionfish, gobies and blennies also show up in the more detailed of the two.

Arcanzil's tide decides more about the dive than its depth does: the current running past the rock swings its visibility from a clear 10 metres down to about 3 on a bad day, wider than the area's general range, and worth checking before you commit to the trip. Under the related name "Gruta do Arcanzil", one diver's account reportedly describes a kelp-lined, canyon-like crack in the cliff face instead of a bare rock top; whether that dive and Arcanzil's rock are the same spot or two nearby features under a shared name is not settled (see FAQs).

Arrábida Experiences, Dive Club Cipreia, MEGA DIVE and Odisseia Azul are Sesimbra harbour operators that list this rock among the dives they run; Anthia Diving Center guided the "Gruta do Arcanzil" dive described above. Water temperature runs around 16 to 20 degrees Celsius; a 7mm semi-dry suit or a drysuit is generally a sound choice for the colder end of that. Bring a macro lens: the one detailed account of this dive spent most of its time working the crevices for nudibranchs rather than looking for anything bigger.