Recent teen death in Florida has been concerned about water safety . But if a swimmer is holding his breath for a long time while exhaling underwater , or is going underwater repeatedly , his CO2 levels are lowered . Ten people die every day from unintentional drowning in the United States . Approximately 10 % of Americans know how to swim , he says . One of the most subtle forms of drowning is a ` ` shallow water blackout ''
Recent teen death in Florida has been concerned about water safety . Ten people die every day from unintentional drowning in the United States . Approximately 10 % of Americans know how to swim , he says . One of the most subtle forms of drowning is a ` ` shallow water blackout ''