  We introduce an Eulerian approach for problems involving one or more soft
solids immersed in a fluid, which permits mechanical interactions between all
phases. The reference map variable is exploited to simulate finite-deformation
constitutive relations in the solid(s) on the same fixed grid as the fluid
phase, which greatly simplifies the coupling between phases. Our coupling
procedure, a key contribution in the current work, is shown to be
computationally faster and more stable than an earlier approach, and admits the
ability to simulate both fluid--solid and solid--solid interaction between
submerged bodies. The interface treatment is demonstrated with multiple
examples involving a weakly compressible Navier--Stokes fluid interacting with
a neo-Hookean solid, and we verify the method's convergence. The solid contact
method, which exploits distance-measures already existing on the grid, is
demonstrated with two examples. A new, general routine for cross-interface
extrapolation is introduced and used as part of the new interfacial treatment.
