Their boxer shorts may have slipped off in the water...
After that happened, Owen would have turned to Woody and said, "Duuuuuuuude, you know those shorts I was wearing? They're, like, you know, GONE!"
And Woody would have said, "They're not gone--I pulled 'em off! You're so wasted, you didn't even KNOW!"
And Owen would have said, "Give 'em back, man!"
And Woody would have held them up in the air and said, "Swim over and get 'em from me!"...