Here's a start
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You just gave me a great idea. A drum that you can fill with water....to different levels...to emulate a deep or shallow shell....in the same drum....depending on how much water you put in there.
With a reservoir to hold the extra water, so you can switch back and forth between different volumes of air inside the shell.
Why do I get the feeling that someone will post the Keith Moon shot where he has a clear floor tom with a goldfish in it?
Thank you cannabis!
This reminds me of the Simpsons Did It episode from South Park.