Could a person scuba diving take off his air tank and use it to propel himself?

So, in my story, in a prelude to an epic aquatic fight scene, my main character gets chased by a great white shark. He swims as fast as he can but he can't escape. Just to clarify, he's wearing one of these types of underwater gear:

He gets an idea that just might work. He takes out his air tank, holds his breath as his helmet fills up with water, and puts his sealed air tank underneath him. He then unseals it and gets propelled straight out of the water. He gets on his boat, gets a harpoon gun and kills the shark.

My question is: would it be physically possible to do that with the air tank?

In most questions, I got a resounding "No" as an answer, so I guess this idea isn't very plausible. But I still want to make my story action packed, so, in future answers, can you provide some sort of alternative?

posted over 6 years ago

MindX‭

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