The Isle of Wight was formerly contiguous with the Isle of Purbeck in Dorset - the Needles are the last remnant of this connection.'
There was a TV programme about Poole Harbour presented by Ben Fogle and the very first shot showed him standing on Agglestone Rock which he claimed is the best vantage point for Poole Harbour.
Agglestone Rock, also known as the Devil's Anvil, is said to have been thrown from the Needles by a giant, often linked to megalithic remains seemingly chucked around at random. It used to be a logan stone, 'aggle' being apparently an old Dorset word that means something like waggle, similar to logan
Agglestone Rock is on top of a cone-shaped mound or tor. Just north is Puck Stone.
Wiki has a reference to Bouldnor where a wooden building was found 11 metres below sea level. They say that this was built around 6,000 BC when the sea was much lower.
An underwater wooden structure, described as an ancient trackway "of possible Mesolithic date", has been partly explored at Bouldnor, near Yarmouthhttp://www.megalithic.co.uk/article.php?sid=23871
Divers found ancient underwater tree stumps in the Solent and evidence of a (Mesolithic?) village. Dating of worked timbers caused some disagreement
Another timber shows signs of having been fashioned as a type of conduit, which is not something that has ever been seen in Mesolithic archaeology before. Some of the worked timbers indicate technological skills that had previously only been associated with the Neolithic era, 2000 years later than Bouldnor.
[Not sure if it's significant but the Cornish name for St Michael's Mount is Karrek Loos yn Koos which means "grey rock in the woods".]