Instantaneous pair potential energy between Water (oxygen) and Backbone

GROMACS version: 2020.2
GROMACS modification: Yes/No
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I have a protein in water, and I would like to know the pair potential energies between each water oxygen and the protein backbone for every trajectory frame to construct a spatial map of potential energy (that, eventually, I will average over time).

I thought that enemat might be the way forward, but as I am a new user, I do not know how to perform the correct selection/grouping that allows me to retrieve the 3d structural information. Any suggestions?