There's some controversy over video showing a 16-month-old swimming unattended.
But the parents said their daughter knows what she's doing, and she is trained.
A certified professional taught Elizabeth Christensen how to kick then flip over for air.
The instruction is geared more towards engaging children's reflexes than actually swimming.
Christensen's father said he understands other parents' concern over seeing his daughter swim solo, but he trusts the lessons. He still keeps an eye on her from outside of the pool.