Endorphins.

Sometimes the world is dark and cold,
and no matter what I'm told,
I'm scared and I'm alone and I'm five years old...
Will you hold my hand?

(...)

Come and take a swim with me,
we'll wait underwater patiently
for the output of endorphins as we're swallowed by the sea
will you hold my hand?
will you hold my hand?
will you hold my hand?

(Dawson, K.)