Yoshi Submarine

From the Super Mario Wiki

The Yoshi Submarine was a form of Yoshi that could be transformed into in Super Mario World 2: Yoshi's Island by touching a Morph Bubble.

The two tasks it performed were travel through bodies of water (because normal Yoshis could not go any deeper into water than the very top), and shoot homing torpedoes (because Yoshis couldn't attack in special forms).

The Yoshi Submarine reappears in Yoshi's Island DS; however it no longer shoots torpedoes.

[edit] Trivia

• Interestedly, in the artwork image in this article; the torpedoes the Orange Yoshi launch actually resemble Yoshi faces at the front while the propeller exists in the back. These types of torpedoes can't be recognized in the game like the artwork, most likely due to pixel limitations.
• Despite the artwork, Orange Yoshi never gets the opportunity to morph into a submarine.

Morph Bubble Vehicles
Yoshi Car · Yoshi Helicopter · Yoshi Mole Tank · Yoshi Submarine · Yoshi Train

Watercraft
Bessie Bass's Battleship | Black Skull | Blackbeard Koopa's Ship | Bowser's Battle Yacht | DK Cruiser | DK's Boat | Daisy Cruiser | Ding Bell | Gangplank Galleon | Hover Craft (DKC3) | Hovercraft (DKR) | Motor Boat | MSS Sea Star | Peapod | Pirate Ship (3 on 3) | Pirate Ship (SSBB) | S.S. Caviar | S.S. Chuckola | S.S. Flavion | SS Tea Cup | Shakedown Schooner | Sinister Star | Sunken Ghost Ship | Sunken Ship | Turbo Ski
Submarines
Bowser's Sub | Doomsub | Knautilus | Koopilus | Marine Pop | Subwarine | Yoshi Submarine