Abstract: The invention relates to an undersea system for the recovery of hydrocarbons, comprising at least one tunnel (13) extending from a terminal ashore to at least one chamber (1) adapted to accommodate drilling and other hydrocarbon recovery apparatus (3, 4).For the purpose of reducing or preventing damage due to a blowout or the like in such a chamber (1) with adhering tunnel or tunnels (13), the system according to the invention comprises in addition to the chamber (1) and tunnel or tunnels (13), at least one further chamber (6) which is adapted to receive and temporarily store hydrocarbons which unintentionally might appear in the first chamber (1) and to emit gaseous or liquid and/or solid hydrocarbon constituents through a tunnel (8) and/or pipe (7) for disposal and/or processing.