How can I get shark skin?

I don't know how far you've gotten in the game but I have the M 700 Sniper rifle silenced, I took a Jet Ski into shark infested waters and waited, I also stayed on the jet ski while waiting for a shark to come near and used aim, scope and breath to highlight the the shark and when you see the sharks fin above water shoot just below and you should kill it in 1 to 2 shots, I killed it with 1 but I'm not sure if you will have the same results...

It's very easy for me.
I just drive jet ski crush a shark (1 hit per kill for normal level) and get the shark skin at under water.

Use a boat, then shoot sharks from the boat , then just dive in and skin them, some boats even have mounted guns so you font even waste ammo