A sea survival device (1) comprising a container (2) with several shells (3, 4) enclosing respective pneumatic liferafts (5, 6) in the deflated and folded-up state, and inflation means; one half-shell (4) enclosing a liferaft (6) is closed by a closure partition (7); the automatically triggered inflation means are operationally associated with at least the first liferaft (5) in a manner such that said first liferaft (5) is inflated first when the survival device (1) is deployed operationally; and the liferaft (6) is operationally associated with inflation trigger means suitable for trigging inflation thereof only once the first liferaft (5) is inflated.