Wasn't the Tor in the middle of marsh back then?

I always thought it was an island. The Bristol Channel as is now came right inland across the Somerset Levels.. maybe the lower levels weren't used for farming as they were prone to flooding.. who knows eh! You can see how far inland the water could have come by sitting onto of Ham Hill in Somerset after a wet winter and looking out towards the Tor... water water everywhere....Tis just my theory and I am probably completely utterly totally wrong so please dismiss it as rubbish... Isn't the legend that Jesus and Joseph of Arimathea (s'cuse spelling) came to Glastonbury by boat, and took the thorn from the top of Wearyall Hill???

I'm going back to Glastonbury at the end of the month, not by boat mind, I'll see what I can find out!!!