  Polar materials can host a variety of topologically significant magnetic
phases, which often emerge from a modulated magnetic ground state. Relatively
few noncentrosymmetric tetragonal materials have been shown to host topological
spin textures and new candidate materials are necessary to expand the current
theoretical models. This manuscript reports on the anisotropic magnetism in the
polar, tetragonal material NdCoGe$_3$ via thermodynamic and neutron diffraction
measurements. The previously reported $H$-$T$ phase diagram is updated to
include several additional phases, which exist for both $H$ = 0 and with an
applied field H$\perp$ c. Neutron diffraction data reveal that the magnetic
structures below $T_{N1}$ = 3.70 K and $T_{N2}$ = 3.50 K are incommensurate,
with a ground state magnetic order that is incommensurate in all directions
with the propagation vector $\vec{k}$ = (0.494, 0.0044, 0.385) at 1.8 K. A
unique magnetic structure solution is not achievable, but the possible single
and multi-$\vec{k}$ spin models are discussed. These results demonstrate that
NdCoGe3 hosts complicated magnetic order derived from modulated magnetic
moments.
