Submergibles ("Deep Apple" in Japan) are little subs belonging to Crash. They appear in the swimming stages of Crash Bandicoot 3: Warped and the Crash Bandicoot N. Sane Trilogy remaster of the third game, where Crash swims through the submerged city of Atlantis. They have torpedoes which can be used to shoot away dangerous sea life and reveal boxes hidden in the coral reefs. They closely resemble fish.
Submergibles are similar to Aku Aku in that they can protect Crash from one attack. The subs immediately explode when Crash is hit by an enemy or hazard. Even if Crash has an Aku Aku mask as well, the subs explode on the first attack, with the Aku Aku mask remaining with Crash. The submergibles are similar to Baby T in this respect.
The submergibles were also going to appear in Crash Bandicoot: The Huge Adventure, where they looked a lot like the ones in Warped, but with a drill on the front, but were cut in the final version.