Eeusk (pronounced "aysk", Gaelic for "fish") is the most consistently praised seafood restaurant in Oban. It occupies a harbourfront position with large windows overlooking the bay and serves langoustines, scallops, haddock, and crab at a level of quality that makes it worth booking well in advance in summer.
The menu changes with what has come off the boats that day. The house speciality is scallops — hand-dived from the local waters and cooked simply enough that the quality of the ingredient does the work. It is not cheap by Scottish standards, but it is good value for what you get. Book ahead for evenings in July and August.