Cob Masonary for wet locations

[Craig Hull]

What materials, other than cement, are suitable for structural use in wet
locations? For example, in building a water tank or swimming pool or
spillway. I'm not asking about waterproof but about structural integrety.
Depending on where we end up and the availability of suitable clay, I
would like to use eathern plasters for the strawbale house we hope to
build someday. But none of the concrete alternatives I've considered seem
suitable for other applications that involved extended contact with water.