Another gene variant that increases the size of the spleen is carried by the Sama-Bajau, nomadic people who live on flotillas of houseboats in the seas off the Philippines, Malaysia and Indonesia.[68] The spleen stores oxygen-carrying red blood cells, and when humans hold their breath it expels these cells to boost oxygen levels; this helps to explain how Sama-Bajau are able to dive to depths of over 230 feet or 70 meters with nothing more than a set of weights and a pair of wooden goggles.