The island also marks the north-western limit of the City of Bristol's water boundary in the Severn estuary.

[1] It is located approximately three miles north of Portishead, midway between Redwick in Wales and Avonmouth in England.

[3] On the 21st of September 1995, Neil Carter from Portishead spent 3 nights on Denny Island to raise money for the RNLI.

[4][5] In 2004, the island was subject to an unsuccessful appeal under Section 6(1) of the Countryside and Rights of Way Act 2000 against it appearing on a map of registered common land.

[6] On the 13th of November 2017, Lave net fishermen from Wales claimed to have discovered a large amount of plastic, some of which was used as nesting material by seabirds, a bomb from WW2, and several cannon balls after visiting Denny Island.