ST. GEORGE'S, Grenada (AP) — An active underwater volcano off Grenada's northern coast called Kick 'em Jenny was rumbling Thursday and regional disaster authorities were put on alert even as they said it posed no threat of triggering a destructive tsunami. Since its discovery in the 1930s, Kick 'em Jenny has erupted beneath the surface of the Caribbean Sea at least 12 times, most recently in 2001. The underwater volcano, which rises some 1,300 meters (4,265 feet) above the seafloor on a steep slope of the Lesser Antilles ridge, hasn't caused any deaths or injuries. Kick 'em Jenny poses the greatest threat to mariners since the gases it releases can lower the density of the water so significantly vessels can lose buoyancy and sink.