Ospreys frequently go completely under water when diving after fish.
This leaves the bird with a lot of very heavy water as excess weight on its body.
They solve the weight problem by shedding the water.
Like a dog, they start at the beak and do a full body, very vigorous, twisting shake back to the tail.
I caught this osprey at the point of the shake reaching his midsection; his beak almost back to its normal position.