Wow foodchain, I don't know what your soil is like...we have mostly sand here, and I wouldn't want to hand dig a hole for an IBC....

Is the sea can for some kind of an underground shelter...?...or are you cutting of the top and making it into a fish tank ? If it's the 2nd one....I wonder if this liner would fit...?
http://www.aquaticeco.com/subcategories ... -Fish-Tank