She's known as the mother of our modern underwater fleet. And, this week, divers have visited the wreak of one of Britain's very first Submarines.
Lying, upright in 30 metres of water - that's 100 feet - the Holland 5 was one of the first submarines accepted for service by the Royal Navy.
She sank 100 years ago and, to mark the centenary, the Nautical Archaeology Society dived to the site - to monitor her condition. Sarah Saunders went on an exclusive journey with them.
Click below to see the video
Our reporter Sarah Saunders on the scene as divers prepare for the murky waters around Holland 5 - one of the first Royal Navy submarines sunk 100 years ago today off the coast of Eastbourne.
Our reporter Sarah Saunders sends these photo as divers prepare for an anniversary dive in Eastbourne, 100 years after one of the first Royal Navy submarines - Holland 5 - was sunk off its coast.
Our reporter Sarah Saunders sends this photo as divers prepare for an anniversary dive in Eastbourne, 100 years after one of the first Royal Navy submarines, Holland 5, was sunk off its coast.