After watching this, you'll realize that lifeguards don't get enough credit.
Look: seconds into this video the child, who loses hold of his raft in a crowded swimming pool, doesn't flail or call for help like you'd expect. The lifeguard sounds her whistle and dives into the pool to save him, but we don't even see him until the rescue is happening.
Something to keep in mind at the pools and the ocean this summer-- the signs are tough to see and trained professionals have to be vigilant. Thank your local lifeguard!