When walking on the beach before he found the penguin, Tom Michell stepped in a large puddle of oil. When he was kneeling at the side of the bathtub cleaning the penguin, the bottoms of his shoes were pristine.
When Tom returns the penguin from the hotel to the sea, he carries it in a handbag. After releasing the penguin, the bag disappears from Tom's whereabouts and is nowhere in the vicinity of the beach.