The Mersey Submarine Mining Establishment was primarily based on two old Hulks, HMS Danoe and HMS Annetin. Until 1904 they were moored in Kings Dock, after which they were moved to Clarence Dock. Liscard Battery was also used for a period to assist with Submarine Mining activities.
K Company of the 1st Lancashire Engineer Volunteers were formed in 1885 with the two Hulks provided as a headquarters in 1886. The detachment went to Milford Haven in 1886 for exercises. In March 1888 the unit was renamed as the Mersey Volunteer Division, Submarine Miners, Royal Engineers. There were three companies with thirteen officers and one hundred and eighty three other ranks. By 1903 a fourth company had been created and the strength increased to sixteen officers and two hundred and fifty nine other ranks. In 1907 the division was converted to Electrical Engineers.
For more on Submarine Mining see here.