Holy scary bathtub, Batman!

So, all of a sudden Logan is terrified to take a bath and it was literally over night that this change happened. Normally Logan would be hard to GET OUT of the bath because he was having too much fun splashing and playing... but the other night (actually about a week ago) apparently he saw a little piece of grass or something in the tub with him and it freaked him out! Robert got it out of the bath as fast as possible and showed Logan that everything was good, but he was still saying 'big bug' and clawing his way out of the tub. Let me add that Logan has never seen a bug in the tub because there has never been a bug in the tub... I don't know why he thought it was a bug in the first place. Since that night he has watched me bathe Hunter and we have shown him that there is nothing in the bathtub. Yet he still acts scared, and we can't not bathe him... I don't know what else to do to help him not be afraid. I've offered to let him shower with me, but he doesn't like the shower. We've tried to have him take a bath with Hunter so he can see that there's nothing to be afraid of, but that didn't work either. I am open to any suggestions here.