Semi-submersible platform

Deepsea Delta semi-submersible drilling rig in the North Sea
Comparison of deepwater semi-submersible (left) and drillship (right)

A semi-submersible platform is a specialised marine vessel used in offshore roles including as offshore drilling rigs, safety vessels, oil production platforms, and heavy lift cranes. They have good ship stability and seakeeping, better than drillships.[1]

  1. ^ "How Do Semisubmersibles Work?". RigZone.