Horsea Island offers divers a wide variety of marine life and underwater attractions organised into 3 zones to avoid ‘diver soup’ with platforms in 2 of the zones for training divers.
Initially, there were two islands, Little Horsea Island and Great Horsea Island. The Navy, needing somewhere to test and develop torpedo's purchased the islands, and joined them together, finally a strip was excavated down the middle to produce a torpedo range of some 800 yards in length, 80 yards wide at one end and 20 yards wide at the other.
The official opening of the range took place in 1889 and it was recognised as being the "finest torpedo experimental range in Europe". Because torpedo's were able to travel further in June 1905 work to extend the range to 1,115 yards in length was completed.