snit, Thanks for your response. I tried to look for an empty drum barrel to make a tube out of one but I wasn't able to find one...
I think that would be one of the most economical choice to make a tube.

Smalma, Thanks for your detailed advise.
My Geoducking trips will definitely require minimum of two people and I'll always be the one to dive in head first to reach and grab those giants.
So that's how I decided on my dimensions.
However, I think 18" diameter & 30" height should also do fine for me and I'll consider your dimensions when I order up a tube.
I looked for either corrugated culverts or commercial grade large PCV pipes but being those items are commercial grade and you have to buy big sticks with high dollar tags...
So I've decided to have one made out of stainless steel at a local welding shop.