semisubmersible

noun3

1. •
   A specialised marine vessel with good stability and seakeeping characteristics, often used in offshore roles such as oil drilling.
2. •
   A tourist vessel that rides low in the water, with the majority of the vehicle submerged, with underwater windows.
3. •
   A low-freeboard vessel, capable of being incidentally submerged, with the majority of the hull located underwater.