The Medway U-boats.
When hostilities ceased on the 11th November 1918, it was arranged for the majority of the German U-boat fleet to surrender at Harwich, the major British submarine base. By the 18th April 1919, a total of 150 surrendered U-boats were moored in lines on the river Stour on the Essex-Suffolk border.
Some of the U-boats were then assigned to the French, US, Italian and Japanese navies. The remaining U-boats were then mostly sold for scrap and were towed to places as far apart as Bo,ness in Scotland and Swansea in Wales.
A list of the surrendered U-boats can be found @ http://www.uboat.net/wwi/fates/listing.html
An eyewitness account of the surrender can be found in chapter 19 of 'A North Sea Diary 1914-1918' by Commander Stephen King-Hall.
Available to view @http://archive.org/details/northseadiary00kingiala
Eight of the surrendered U-boats are listed on uboat.net as going to the Medway.
U 112, broken up Rochester 1922.
U B76, ditto
UB 93, ditto
UB 144, ditto
UB 145, ditto
U 126, broken up Upnor 1923.
U 141, ditto
UC 60, broken up Rainham 1921.
Note, broken up must refer to the date at which Mr Batchelor sold the hulls for scrap.
From 'WW1 Medway U-boats', by Pat O'driscoll. After the Battle, number 36, 1982."A number of correspondents told me about Mr. Albert 'Spot' Batchelor, who owned a small private cement works up-river at Halling, later taken over by the Rugby Portland Cement Company...........
.......In 1914 his cement works at Halling was driven by a steam-engine. About 1919-20 he brought a number of U-boats and took the engines out of them. The machinery of the submarines (wrote a correspondent who preferred not to be named) consisted of a 700 hp MAN diesel engine for main propulsion, two 490 hp manually reversible engines and 230V Siemens generators.
Two of the bigger motors went to replace the steam-engine at his cement works (unfortunately they were scrapped before I started to investigate). Two more went to the Holborough cement works at Snodland (established 1926). Southend Corporation bought two from him for the local power station and they saved the town from blackouts on a number of occasions. A further two, complete with generators, supplied power to the Wembley Exhibition of 1924 while a pair went to Davantry for the famous 2LO broadcasting station. Two even went out to New Zealand for use in the building of a hydro-electric project.
Mr. J. R. Kerr, who was then a small boy, recalled to me how he would earn a penny-and a look at a former U-boat engine in action-by delivering the Sunday dinner of the engineer on duty at the Municipal Power Station at Gillingham.
Mr. P. Squires, of Hoo, actually saw the three submarines arrive at Stoke Mud Hole, towed by Knight's tugs Kenley and Kent............
Mr. Squires and other boys crept aboard the big submarine. By then, he said, the engines had been removed and in the space left there were a number of 15ft pontoons................... He recalls that many submarines were broken-up at Lower Upnor, further upstream, and that the two submarines in Slede Creek were broken-up at the beginning of the war when scrap fetched good prices.
Mr. Norwood sent me a photograph of one of the smaller U-boats taken in the 1930's. They lay bow-on to the saltings and apparently they were without conning towers.............
A reader at Gillihgham, Mr. L. A. Griffith, who took a great interest in unravelling the U-boat story, very kindly followed up many of the leads given by correspondents and consulted Admiralty Disposals files at the Public Record Office. One man who wrote to him spoke of helping to dismantle several U-boats at Halling including one big one that was U 112."
So it seems that the eight U-boats were sold to Mr. Batchelor, who had them towed up the Medway to his cement works at Halling. Here the main and auxiliary engines were removed. The hulls were then sold to the ship-breakers, possibly the Upnor Ship-breaking Company.
5 were scrapped. When the price of metal fell, or the Upnor Ship-breaking Company went bust, the three remaining hulls were dumped on the mud banks of the Medway at Humble Bee Creek and Slede Ooze. During the early 1940's, the two boats in Slede Ooze were scrapped, leaving just their very bottoms. For some reason the boat in Humble Bee creek was left untouched.
So, to my way of thinking, the remains of the three U-boats must be from the eight listed above. Note that all three seemed to have had their conning towers removed, possibly to allow them to be taken under Rochester bridge.
Uboat.net lists 5 U-boats that "ran aground on the English east coast on the way to be broken up."
This could be anywhere between Berwick to Dover. I would discount these, along with U 122 and U 123, on account of Mr. Squires as quoted above, which suggests that the U-boats were deliberately dumped.