 In traditional tales the blue men have the power to create severe storms , but when the weather is fine they sleep or float just under the surface of the water . They swim with their torso from the waist upwards raised out of the sea , twisting and diving in a similar way to a porpoise . To amuse themselves the creatures play shinty when the skies are clear and bright at night . They are able to speak and converse with mariners and are especially vocal when soaking vessels with water spray , roaring with laughter as vessels capsize . 
