In some phases projects can seem nearer civil engineering than anything else. For this reason many projects have adopted the techniques and proceedures used in the inshore and offshore commercial diving industries. One of the first to do so on a large scale was the Mary Rose Project. The success of this eclectic approach led to similar systems being deployed elsewhere. However, most sites that used this sort of equipment were relatively shallow.
Increased depth brings other factors into play.
In 1994 the opportunity to record a wreck on the limits of the air-diving range. This site is the wreck of ship believed to have sunk in 1525. However, limited 'productive' bottom time, narcosis and the safety implications of repeat air diving in cold water were all good reasons for another solution. A system was needed that would be both safe and archaeologically productive. The first requirement was a diving support vessel and the project was fortunate to secure the loan of Nigel Boston's Terschelling.