Registering a ship has always been to prove its nationality. For Merchant/Pleasure ships Part 1 identification it is essential for overseas voyages. Another reason for Part 1 registration is to use the ship as security to obtain a marine mortgage which in turn is registered.
Purchasers of UK registered ships can obtain a Transcript of Registry which shows the registered owners of a ship and whether there are any out standing Mortgages against that vessel. Tonnage surveys typically consist of an in the water inspection whereby a number of specific measurements and registration details of your particular vessel are recorded.
This is then used along with other documentation to provide the vessel with a formal Part 1 registration. Rea Associates carry out these measurements on behalf of the RYA and the MCA.