A navigation aid maintained by D sank. and disappeared. D issued a bulletin and told seamen that the aid was not at the bottom of the channel. P brought suit against D under the Federal Tort Claims Act for damages suffered to his vessel while navigating in the Wrangell Narrows south of Petersburg, Alaska from a collision with the 'missing' navigation aid. The aid had submerged and disappeared beneath the surface of the channel waters leading into Petersburg. P alleged that D was negligent in its operations to locate the submerged navigation structure. After the close of evidence, P moved to amend the complaint under 15(b). P wanted to raise the additional claim to relief based on the 'willful, wanton, or reckless conduct' of D. P contends that 'the amendment goes to matters which have already been in proof and D cannot possibly be prejudiced by this amendment, since any effort which it would make to show lack of willful, wanton or reckless care would be no different than its efforts already made to show lack of negligence on the part of D.'