The Legend of the Sea Dragon
Legend has it that the greatest Scottish warrior of all, Fionn mac Cumhaill - also known as Fingal (as in the famous Fingal's Cave) - was walking across Islay with his two massive hounds, Bran and Seeolang. Fionn, who was possessed of supernatural powers and superhuman strength, hoisted a large standing stone and threw it half-way across the island - into the depths of Loch Indaal - for his dogs to fetch back.
The splash made by the stone stirred the sea-dragon Kranna Dubh from his thousand year sleep in the deep. Kranna surged up and swam to the shore at Bowmore to meet with Fionn in combat. A fierce battle ensued, ending with Kranna lurching back into the Loch, mortally wounded by Fionn's magical sword, Mac a'Luin, his dark blood seeping into the waters.
It's said that when the sun sets, Loch Indaal turns red with his blood - and that local mothers scold their children severely, if ever they catch them pitching stones into the Loch. (Besides which, we wouldn't want anything to disturb the quiet maturing of our whiskies in their Loch-side vault.)