 The crossing was complicated by the fact that, apart from six hours a day around high tide, two-thirds of the passage was through a channel between the English Stones and the Dun sandbank through which the ebb tide flowed so quickly that "a passage [could not] be made against it except in strong and favourable winds".Even after leaving this channel the ferries had to then cross the head of another channel, the Shoots, through which the current was so strong that they were often pulled down it by the ebb tide