For a long time it had been thought that Cervera would try to escape from the harbor, in which he could not be reached because of the strong forts that protected the entrance. To bottle him up more effectively, the Americans tried to block up the harbor entrance by sinking an old iron steamboat, the _Merrimac_, in the channel. This heroic work was undertaken by Lieutenant Hobson with a crew of seven daring men, but the plan failed, for the _Merrimac_, instead of sinking where intended, swung to one side of the main channel.