  2-group global symmetries are a particular example of how higher-form and
conventional global symmetries can fuse together into a larger structure. We
construct a theory of hydrodynamics describing the finite-temperature
realization of a 2-group global symmetry composed out of $U(1)$ zero-form and
$U(1)$ one-form symmetries. We study aspects of the thermodynamics from a
Euclidean partition function and derive constitutive relations for ideal
hydrodynamics from various points of view. Novel features of the resulting
theory include an analogue of the chiral magnetic effect and a chiral sound
mode propagating along magnetic field lines. We also discuss a minimalist
holographic description of a theory dual to 2-group global symmetry and verify
predictions from hydrodynamic descriptions. Along the way we clarify some
aspects of symmetry breaking in higher-form theories at finite temperature.
