The Castoro Sei (Italian for Beaver Six) was a column-stabilized semi-submersible pipelay vessel.

[1] The firing line comprises the fixed pipelay ramp, enclosed in the central housing, running along the longitudinal centreline of the vessel.

It is connected to an internal and external ramp, both of which have adjustable inclination to facilitate pipelay in varying water depths.

A ramp extension unit is available for use in deep water or for severe seabed conditions.

[1] The Castoro Sei was built in 1978 by Fincantieri at Trieste yard, and was owned and operated by Saipem.