I would get out if it was a dangerous species and a dangerous size, if it was small 4 or 5 foot i would shoot it in the head.
This is not me, but just to give you an idea of what i am talking about.

The best defence is a good offence. BTW do those shark shields work? I think if it wanted to take a bite out of you that shield would do nothing to stop it, if it was just checking you out then it would work though. The thing is that most always sharks will come to check you out before they take that 'taster bite' they are very smart and i guess want to see if we are even edible before they take a nip out of us. Have you had any close shaves with sharks since you had the shield??