streetpiracy:

Glen Fox

Sharks continued to feed until it appeared they experienced
what we believed to be post-porandial torpor. For example, over
long feeding bouts (.6 hrs), shark would continue to feed to the
point where they would cease lifting their heads above the
waterline. Moreover, they would continuously bump the carcass in
what appeared to be an attempt to feed, but despite mouthing the
carcass, sharks were unable to achieve a sufficient bite to remove
flesh, after which they would simply bounce off the carcass and
slowly sink underwater.

White Sharks (Carcharodon carcharias) Scavenging on Whales and Its Potential Role in Further Shaping the Ecology of an Apex Predator

-http://www.apexpredators.com/images/stories/research/journal.pone.0060797.pdf