  Sr$_{3}$Cr$_{2}$O$_{8}$ consist of a lattice of spin-1/2 Cr$^{5+}$ ions,
which form hexagonal bilayers and which are paired into dimers by the dominant
antiferromagnetic intrabilayer coupling. The dimers are coupled
three-dimensionally by frustrated interdimer interactions. A structural
distortion from hexagonal to monoclinic leads to orbital order and lifts the
frustration giving rise to spatially anisotropic exchange interactions. We have
grown large single crystals of Sr$_{3}$Cr$_{2}$O$_{8}$ and have performed DC
susceptibility, high field magnetisation and inelastic neutron scattering
measurements. The neutron scattering experiments reveal three gapped and
dispersive singlet to triplet modes arising from the three twinned domains that
form below the transition thus confirming the picture of orbital ordering. The
exchange interactions are extracted by comparing the data to a Random Phase
Approximation model and the dimer coupling is found to be $J_{0}=5.55$ meV,
while the ratio of interdimer to intradimer exchange constants is
$J'/J_{0}=0.64$. The results are compared to those for other gapped magnets.
