Meghan Castellano was born and raised in the quintessential surf community of Oceanside, California. Her father was a respected Colonel in the United States Marine Corps who worked as a training officer. Her mother was a researcher at a nearby biotech company. From an early age, she was known as a high achiever in math and science and as an athletic prodigy. An Olympic hopeful in the 200-meter breaststroke, Castellano split her time between the pool and the army base.