Cassette assembly, waterborne vessel and method of servicing a water-accessible structure

A cassette assembly 200 is attachable to an end portion 102 of a waterborne vessel 100. The cassette assembly includes a cassette section 210 to bear against an external structure (300, Fig 5A) in use. The cassette section is movable relative to the vessel in a direction towards an opposite end of the vessel. A resilient buffer system 250 counters movement of the cassette section when the vessel is moved towards the external structure, wherein the resilient buffer system includes a fluid-operated buffer 251. A waterborne vessel including a receiving portion 120 for receiving the cassette assembly is disclosed and can be used to service a water-accessible structure such as a wind turbine.