The tunnel develops in the same way of the coast at a maximum depth of 39 metres. After ten metres from the north entrance, an hydrothermal spring (one of the deepest we know) flows. The vault Is full of fan bryozoans Hornera frondiculata and mermalds' vell Sertella sptentrionolis. Also the sponge crab Dromia personato and the cave spider crab Herbsba condyliata lives here. The bottom of the middle part Is covered with Neptune grass Posidonia oceanica dead leaves. We arrive at the southern entrance atrium where big blocks lay. This place Is very nice with columns and stalagmites among with the boxer shrimp Stenopus spinosus, with white long antennae lives. On our heads the cylindrical chimney gives the name to the dive. We have three possibilities: going back through the tunnel, passing through the chimney or going out through the south entrance. In a precise place we can see the feather duster worm Bispira mance and the uncommon seaweed Fauchea repens. In open water fish of passage.