Recently, a company created a fascinating toy available to the sufficiently rich. It is not hard to imagine that military types have taken a close look at this, and have thought about ways to tweak and expand the idea, possibly to be deployed from something like the stern-gate of a Wasp-class ship. Each "submersible fighter" takes a crew of one or two pilots, has an array of active and passive sensors, and is armed with up to four mini torpedoes. They are also very stealthy- if detected at all, one would easily be mistaken for a flatulent beluga whale.
Now we make the leap from reality to fantasy. Two belligerent entities have each developed these small submersibles. The submersibles patrol around and under their carrier searching for the enemy. Their weapons might not be powerful enough to blow a large ship out of the water, but can certainly twist up its propellers and rudders and leave it crippled. But occasionally they encounter each other, and a dogfight ensues. What will that dogfight be like?
Certainly, it won't be like the submarine versus submarine combat of WWII, nor the cold war cat-and-mouse games, which is very slow and methodical; it can last hours, even days. Likewise, it won't be like the high-speed high-g affair of aerial dogfights, not even that of the Sopwith Camel versus Albatross days.
How will the submersible pilots act in this situation? What maneuvering will they do? Which sensors (sonar, IR, MAD, electroreception) will be most useful?
NOTE: Entered as part of the fortnightly challenge.