If you think reapplying sunscreen at regular intervals is a lifeguard’s most fine-tuned skill, this video will change your mind.

Lifeguard Rescue posted an 84-second clip from Whirlin' Waters Adventure Park in North Charleston, SC, which shows an eagle-eyed lifeguard at a crowded wave pool see something that no one else does: a drowning child.

It takes her only a single second to see the child slip out of his inner tube and struggle to resurface, then respond accordingly.

[h/t TIME]