Marine biologist Austin Gallagher was boating in the vast sea surrounding a string of tropical islands, Florida Keys, on November 13, 2010. Together with his team, they were able to pull an 8-foot-long tiger shark out from the ocean and into the boat to tag it with a satellite tracker. Suddenly, while Gallagher was trying to take its measurements, he "just saw a huge plume of feathers explode on the back of the boat". Apparently, the shark had puked some 8- to 9-inch-long feathers!
Why do sharks do this? Well, when sharks are stressed out, they barf - even to the point of puking their entire stomachs out. Thing is, some sharks (like tiger sharks) tend to just gobble down whatever is within reach (i.e. bird feathers). So, when facing a stressful situation like what happened to the tiger shark, its instant reflex would be to immediately get rid of whatever foreign food it is inside their gut.
As to puking their guts out, (which by the way has a scientific name, stomach or gastric eversion), this instinct is a way for them to cleanse their stomachs. “It’s basically rinsing it out,” Gregory Skomal, a senior scientist at Massachusetts Marine Fisheries, says.
And while this sounds very dangerous, sharks can actually survive the procedure. They can just retract its stomach back into its body in less than a second and would swim as if nothing happened. Look:
There are those number of sharks that aren't as lucky, however. Like this beached blue shark in Provincetown, Massachusetts.
And while this is believed to be common, such behavior is ironically rarely seen. Hence, it is difficult to confirm exactly why it happens. “These really unique instances ... provide us insights into the secret lives of these animals,” Gallagher says. “I kind of felt honored that I’d finally been able to see something like that.”