An internet forum post on trying to get pictures of feeding Brown Pelicans – Pelecanus occidentalis got me to pull out these pictures of the behavior.  None are particularly great photographs but, they do illustrate the events.  The pelican begins with gliding over the feeding ground.  When prey is spotted, it puts it’s neck into an ‘S’ shape and rolls into a dive.  Just as it nears the water, the neck strikes forward like a snake, making a very clean entry.  Notice that the beak is upside down so that the pouch is the top of the bill as it enters.

With the neck extended, there is almost no splash until the body and wings hit the water.  But, the pouch is opening quickly with the force of the water.  That stops the head and the neck curves again to absorb the shock and the pelican flips upright.

When the pelican dives in, the pouch is opened by the force of the water and spreads out like a parachute or castnet.  The two pictures below show this about as well as possible.  The first shows the pouch with the pelicans head fully immersed.  It is heavy with water at this point and, with luck, some fish.  The pelican settles on the water and then slowly lifts its head as the pouch drains.

As you can see in the second it is still very full.  As usual, just click on any of the images for a larger version.