Diving and surfacing floats provided useful means for ocean measurements. A new diving and surfacing float (pop-up float) is developed by using an electro-chemical engine. It dives with its own weight, and surfaces with buoyancy of oxygen and hydrogen gases produced by electrolyzing water. When oxygen and hydrogen burn by lightening and change into water, the float can dive again. Therefore it can dive and surface repeatedly. The production of oxygen and hydrogen with electlysis of water and their burning by lightening make a completely closed cycle, and there occured no broblems like waste gas. The preliminary tests were conducted in the sea of the depth of 33 meters and their results were disscussed for practical applications of the float.