This film illustrates the British emphasis in film to tell a story by "showing" through body language, countenance, and character development rather than "telling" through dialogue. In a dinner engagement between Emily Mortimer and Bill Nighy, the dialogue is sparse and there are moments it appears one might speak but refrains; yet, when the scene ends, a viewer may realize that their failure to speak bespoke their feelings more accurately than any words.
If you like, quiet films, with action that drifts like the waters in many scenes, you may enjoy this one. The only special effects are those the acting may affect within the viewer.