HMS Magpie on sea trials last year (Picture: Royal Navy)
HMS Magpie may be the second smallest vessel in the Royal Navy's fleet, but this summer she has a big job.
She has just arrived in Portsmouth to carry out bathymetric survey work to keep new aircraft carrier HMS Queen Elizabeth safe.
She will spend three months surveying the sand and mud on the seabed at Portsmouth harbour, as any shift could cause a threat to the aircraft carrier.
More than three-and-a-half-million cubic metres of clay, sand and gravel was removed from the harbour to accommodate HMS Queen Elizabeth.
The survey will check there has been no change in the seabed and it is ready for the arrival of HMS Queen Elizabeth's sister ship HMS Prince of Wales, which should arrive later this year.
Portsmouth Harbour is one of the busiest in the UK, seeing more than 230,000 vessels come and go throughout the year.
HMS Magpies naming ceremony in June 2018 (pictures: MOD)
This is only the second mission carried out by HMS Magpie, which joined the Navy last year.
Before heading to Portsmouth the boat was surveying the waters around Barrow-in-Furness, where the nation's nuclear submarines are built.
Her built-in sonar system allows the crew to scan every inch of a harbour's seabed and provides a 3D image of what is hidden beneath the surface.
HMS Magpie replaced HMS Gleaner, which retired last year after 35 years of service.