Pentillie Castle was built on the banks or the River Tamar in 1698 by James Tillie. It was adapted in 1809 into a castle and then reduced in size in 1968. It has been recently restored into a venue suitable for Weddings, corporate meetings and conferences, as well as relaxing holidays.
Here you can see the Boat House on the River Tamar. Unfortunately, when I had the opportunity to take this, it was low tide, so hence the large mud banks. When the tide is in, it does look so much better.
See http://www.pentillie.co.uk/ for more details.