are "at."

Diving is certainly the best way for you to enter the water--always
provided that you know all about its depth. Nothing can be more
unhealthful than the dawdling habit of wading out ankle-deep or
knee-deep, and waiting to get your courage up. The hot sun beats down on
your head. Your feet and legs are in the cool water whose temperature is
anywhere from ten to twenty-five degrees lower than that of the air.

You can't remain long under these conditions without injuring yourself.
Nature's plan is to have the head cool and the extremities warm. Go
contrary to this, and you are in trouble. Probably most of you can
remember having had a headache some time or other from this very cause.
Indeed, physicians will tell you that many attacks of cramps in the
water are due to the swimmer's foolish habit of wading in very slowly.
Deranged circulation causes cramps. In places where it is not safe to
dive you can easily stoop over and throw a few handfuls of water on your
head. Then hurry forward and throw yourself in--fall in. Will other
fellows laugh at your precautions? Well, let them laugh, and pay for it
with the twinges of cramps. I have been swimming twenty years, and I've
never had a cramp, simply because I've followed the rules laid down
here.

Never let yourself be frightened in the water. A boy I know found
himself far outside of the breakers at Cape May. He swam deep--that is,
with his feet far below him--and found that in spite of his efforts he
was making no headway, or very little. Instead of howling for help, and
using up his strength in struggles that would drown him before help
could arrive, he put his wits to work. He soon found that the off-shore
current was below the surface, and that at the very top of the water the
flow was toward the shore. Thereupon he drew up his legs and swam as
near the surface as he could. Even then it was a long swim for a
twelve-year-old boy, but he got the beach under his feet at last.
Another boy I know was dragged far out by a "sea-puss" at Long
Branch--one of those deadly, swift, sudden currents that pounce on a
bather unawares and carry him away from shore. This boy waved his arm
and shouted for help. When he saw the men on shore running toward a
surf-boat he calmly turned over on his back and devoted all his energies
to floating. He had been carried nearly a mile before he was rescued. If
either one of these boys had been frightened he probably would have
drowned.