Cala Ferriol

The boat moors between two small islets, attention turning to the larger of the pair. Drop down the sheltered inside face to about 12 m and the wall opens into a crevice that becomes the tunnel entrance. The tunnel is about 30 m long and up to 15 m wide — broad enough that the walls stay out of fin range, and natural light enters from both ends. Red coral and sponges cover the brighter sections. Lobsters sit in the cracks. Conger eels watch from holes. The exit drops divers at around 26 m into a small canyon that runs northeast to a sandy bottom at ~29 m, where stone blocks break up the seabed. The deep extension is optional. Most divers turn at the tunnel exit and start the ascent. The shallow return runs the islet perimeter at 5-10 m, passing octopus holes and eel crevices on the rocky face before surfacing at the boat.

Most overhead features on the Costa del Montgrí ask something of the diver. La Pedrosa's tunnel is longer and starts at 18 m, with an exit at 24 m and a chimney shaft running up the middle. The Cala Viuda cave cluster is a 200 m system with multiple passages and three air chambers, requiring a guide. Cala Ferriol is the simpler version — a single straight tunnel, wide enough to swim through without thinking about the walls, lit from both ends, with the entrance in OW recreational depth. For first-time tunnel divers it is the coast's introductory swim-through. For experienced divers it works as a relaxed second dive after deeper morning work at Reggio Messina at 32 m or Marmoler at 42 m, both on the same boat circuit. The cove itself stays quieter than the Medes islands a few kilometres offshore.

Coast operators run a 25-minute boat ride from L'Estartit to the mooring between the islets. Anchoring is not permitted in the cove; mooring buoys handle this — yellow buoys reserve for dive-centre boats and free blue buoys take boats up to 9 m. Buoy use runs sunrise to sunset only. Bring a torch even though the tunnel is naturally lit; it brings out the colour on the red coral. The sandy floor silts under fin strokes, so trim and slow finning matter inside the tunnel. Tramontana (N/NNE) is the wind that cancels coast diving; heavy easterlies expose the cove from the open-sea side. For the optional extension to 29 m at the post-tunnel sandy seabed, plan EAN32 if your training supports it.