The English dub title for this episode is a reference to the saying "Man overboard!"
Ash and his friends meet Luka.
Coral, real-life animals, are visible underwater. This is also the last episode to contain real-life animals until Fish Up the Golden Koiking!! (2014), 607 episodes later.
This is the second episode after Rougela's Christmas (1998) where someone uses someone else's Pokédex. In both cases, it was Misty using Ash's.
When Luka says Misty's treasure map theory isn't too far off, Brock and Misty suggest "Gold and Silver, Pearls and Diamonds"; all titles of Pokémon games, two of which were not released at the time.