  In this paper we parallel the construction of Tong of a gauge theory for
shallow water, by writing a gauge theory for the Euler fluid in 2+1 dimensions.
We then extend it to an Euler fluid coupled to electromagnetic background. We
argue that the gauge theory formulation provides a topological argument for the
quantization of 2+1 dimensional Euler Hopfion solution. In the process, we find
a (non-gauge) action for the Euler fluid that can be extended to any dimension,
including the physical 3+1 dimensions. We discuss several aspects of the ABC
flow.
