Premise: Molly could swim like a duck , and quite covered herself with glory by diving off the pier .<br>Jack undertook to teach Boo , who was a promising pupil , being so plump that he could not sink if he tried .<br>Jill was soon through , and lay on the sand enjoying the antics of the bathers till she was so faint with laughter she was glad to hear the dinner-horn and do the honors of the Willows to Molly , whose room was next hers .
Hypothesis: boo was plump he could not sink