mouthful

He swallowed a mouthful of sea water when he fell in.

“Unquestionably his metabolism is unduly susceptible to stresses resulting from the interaction of external excitations,” he said, and Bobbie patted him on the shoulder in a maternal sort of way, a thing I wouldn't have cared to do myself though our relations were, as I have indicated, more cordial than they had been at one time, and told him he had said a mouthful.

“She sells sea shells” is a bit of a mouthful to say.

to give someone a mouthful