Loch Coruisk is only a small height above sea level and can be accessed by boat [regular service in reasonable weather] from Elgol, itself accessed by bus from Broadford. Alternately it can be reached on foot, from Elgol via Camasunary with a bit of a scramble on the 'bad step', or by a fine walk through the Black Cuillins from Sligachan. This warning will appear on any page concerned with walking in the Cuillins - compasses are not reliable here and mist can fall quickly.
The Loch itself is magical. Except for its short outlet to the sea, it is practically surrounded by the steep, shapely, volcanic gabbro peaks of the Black Cuillins. I cannot recommend it too highly.