When Spring falls into the seagull eggs she creates a wet patch or her right buttock. When we next see it as she walks away, it is very much larger.
When Spring almost falls overboard when Ashton's line slips out of his hands, a water mark is created on Spring's shirt. The pattern of the water mark changes between the close-ups and the long shots.
After Spring and Ashton swim in a race from the sailboat to emerge on the beach, Spring's hair is wet, while Ashton's is dry.