On "Seinfeld," the distressed whale in "The Marine Biologist" has a golf ball lodged in its blowhole.
The golf ball comes from Kramer's misguided attempt to hit Titleist balls into the ocean at Rockaway Beach. George later discovers the stranded whale and, pretending to be the marine biologist Jerry claimed he was, performs an improvised rescue. He reaches into the whale and removes the ball, then delivers the episode's famous dramatic monologue about the "white whale."
The joke depends on the absurd connection between Kramer's earlier golf-ball scheme and George's accidental heroism. The ball is not a baseball, tennis ball, or marble; those options are plausible only because the episode never shows the object in a conventional close-up. The episode originally aired on February 10, 1994, as the 14th episode of season 5. The climactic whale speech was reportedly written very late, giving Jason Alexander little time to rehearse it.