Arvoredo Marine Reserve

Everything here is a boat day and the boat leaves early. Operators run out from Bombinhas and from the beaches at the north end of Florianópolis, on half- or full-day trips built around two dives, with the surface interval anchored in the lee of an island. Access is controlled rather than open: you book through an authorised centre and dive where its authorisation allows, so this is not a coast where you turn up at the harbour in the morning and negotiate a boat.

The islands are granite domes, which underwater reads as big rounded boulders stacked into slopes and short vertical faces, with sand channels running between them. The sheltered northern ground is gentle and stays divable in most conditions, so it absorbs the bulk of the traffic and is the fallback whenever the southerlies are up; the more exposed sites are deeper and want a calm day. The islands have been protected since 1990, and divers tend to notice it first in the size of the resident groupers.

Because wind decides whether the boats run at all, most people build slack into the plan. Booking a two- or three-day window instead of a single fixed date is the standard local approach, and centres will usually roll a cancelled trip forward. The reserve suits divers content with structure, big resident fish and cold-water invertebrates rather than coral colour, and it works as a two-day addition to a trip already heading for Florianópolis or Bombinhas. Bring more thermal protection than the latitude suggests, because the water at depth runs colder than the beach weather implies.