The message
from enigma contains these words:

it would take a couple years, but a kid can drown in less than
an inch of water...

A toddler can drown incredibly fast, see below.

how deep is the pond, what dimensions &
how stupid are the kids?

It's nothing to do with intelligence.Small children are more
susceptible to shallow drowning (and smothering face-down, and just
stopping breathing) because it takes several years for the immature
human brain to develop automatic breathing reflexes.

Janet.