That looks like Rendered mode. Switch to Raytraced to see inter-object reflections. Rhino Render uses the same engine as Raytraced so once you render you also should see them.
Assuming you’r using Rhino 7 I’d actually use a Physically Based Material. I have posted a couple on this forum that you may want to use, let me find the posts for you.
Addendum: turns out I made already a list in another post: Sea / ocean material, bump and displacement not showing - #2 by nathanletwory, and here a simple scene by myself with oceanic water Raft on Sea 