Diving Support Vessels (DSV) are vessels that facilitate diving - normally saturation diving.
The vessel can be both a monohull (a regular ship) or semi-submersibles (drill rigs). Each type has its advantages,
monohulls have rapid transit speed, while semisubmersibles have great deck capacity and stability.
In addition to a saturation diving spread, most DSVs are equipped with a heave compensated crane (100-odd tonnes), ROVs and possibly an air diving spread (for shallow dives down to -30 m). This makes it a more versatile ship capable of performing several different construction tasks. The downside is that it becomes more expensive to hire the more equipment you place onboard - and you can end up no work by pricing yourself out of the market.
A saturation dive spread often consists of at least the following items:
- Two dive bells
- Two bells gives good redundancy in case one bell fails when at depth. Divers usually appreciate a way home. Sending down another bell to them usually does the trick.
- Observation ROV
- Some countries require that the divers are under observation at all times. An obeservation ROV does the trick. The ROV can also check things outside the divers excursion zone.
- Life support tanks
- Often three tanks are used to "store" the divers in when they don't work. Two teams share each tank, giving 24 hours diver coverage with 2 tanks, and two teams in decompression in the final one. Divers can transfer from any tank to any bell.
A DSV monohull typically house approx. 100 people, working 12 hour shifts 24/7.
Your mileage may vary concering what kind of cabin you recieve onboard :)