Question to the Department for Transport:

To ask the Secretary of State for Transport, what guidance exists to define (a) sunk", (b) stranded and (c) abandoned vessels for the under the terms of s.252 of the Merchant Shipping Act 1995.

Guidance can be found here https://www.gov.uk/guidance/wreck-and-salvage-law. Local port acts may contain additional definitions that may vary from act to act.