Looks like a shark egg

Got this along with a feather duster. It looks like a sponge but not really, as well as some kind of shark egg.
When I took it out of the water, some water did squirt out.
Any ideas?

 

Probably the Black Banded Cat Shark Cat Shark, if it is a sharks purse/egg you should leave it submerged

 

Thanks I do have it submerged. Had a bamboo shark egg once.
I will keep an eye on it for devolpment.

 

Definitely a shark egg. Keep mild flow to the egg as well. I hatched one and kept the shark for over a year. Syringe fed it for two weeks until it took squid from my hand and after that he ate every 3 days. He now resides at the Tampa aquarium in the petting exhibit. I miss him, the most interactive guy in my tank.