Alfred Francis Blakeney Carpenter,
The Blocking of Zeebrugge
“ Allowing six feet as the minimum depth required to float small naval craft, it will be seen that the upper portion of each blockship should reach to within six feet of high tide level, or, at least, nine feet above low tide level, when resting on the bottom. The height of the blockship's hull, therefore, would need to be equal to the depth of the sea at low tide level plus, at {49} least, nine feet. Now, the choice of vessel is naturally limited. In the midst of war it is unlikely that a navy would possess many craft, if any, which were not already in use for other purposes. ”
