Surface attackers among amphibious shipping

Had enemy surface ships actually attacked amphibious operations?

Yes. Exercise Tiger is one example, and the vulnerability of landing ships made preventing such attacks a major naval concern.

Exercise Tiger provides an example of enemy surface ships reaching an amphibious operation. Landing and supply vessels could not withstand cruiser shells and torpedoes. Once attackers reached them, they could destroy vulnerable shipping faster than escorts could stop them. Rescue work would also divide the escorts' attention and expose them to attack. Keeping enemy surface forces away was therefore a major concern even when such attacks were infrequent.