  We give a geometric formulation of 3D incompressible Euler that contains the
Eulerian and Lagrangian gauges as special cases. In the Lagrangian gauge,
incompressible Euler is a real analytic ODE in Banach space; a short proof of
this known result is given. We then describe (in a self-contained section) some
basic properties of a hypothetical self-similar solution to 3D incompressible
Euler.
