The chances of rescue must bear some relation to the numbers to be rescued. For this reason it was decided to disembark the oversea passage crews from each blockship before arriving within the danger zone. [Sidenote: Motor Launches for Rescue Work] When the question arose as to which of the motor {89} launches should be used for effecting the rescue of the crews from the blockships, volunteers were asked for. In spite of the almost incredible difficulties and tremendous risk involved the number of applications for this dangerous task was most embarrassing. Eventually lots were drawn and the winners were greatly envied by their less fortunate confrères. The organisation necessary to ensure efficient co-operation, and co-ordination of effort, was no small matter. Every vessel, however small, had important duties to fulfil. At any moment during the operation success might depend on the action of a single unit: it would be difficult to conceive any circumstances where the value of initiative would be more pronounced. Nothing could be left to chance--any suggestion of possible failure was unthinkable. {90} CHAPTER VII MATTERS AFFECTING THE PASSAGE. THE SUPPORTING FORCES. THE GERMAN SEA-FORCES. THE PREPARATORY WORK Safe passage across the seas, especially from the navigational point of view, provided much food for thought. The liability of new shoals to form and of old shoals to move their position, the consequent lack of dependence on the charts, and the absence of the usual navigational aids have already been mentioned. These navigational difficulties, increased by the low visibility which obtains at night, combined to form the first of the three main obstacles to be encountered in blocking operations of this nature, namely, the difficulty of locating the destination. Considerable amusement was caused in naval circles, subsequent to the operation, when a certain individual, from another country, published a special piece of "inside information," to wit, that the method whereby _Vindictive_ reached Zeebrugge Mole was a great secret, known only to Captain Carpenter and one other, involving intricate calculations in connection with astronomical phenomena. I was extremely interested in this suggestion for it was the first that I had heard of it. As a matter of fact the safe navigation was largely the outcome of a very fine piece of work by two officers specially lent from the Hydrographic Department of the Admiralty.[1] [1] Captain H. P. Douglas and Lieutenant-Commander F. E. B. Haselfoot. {91} The major portion of the area through which the various forces were to pass was surveyed under great difficulties. [Sidenote: Object of Special Survey]