DO NOT UNDER ANY CIRCUMSTANCES PICTURE ANYONE NAKED.
Ahem.
It sounds cliche but concentrate on breathing. I had similar troubles, I could write a decent speech but my nerves got the better of me every time. My hands shook like a hypothermia victim and my throat was as dry as the humour I attempted.
Making sure my speech flowed definitely helped. If as you're reading through it (preferable aloud) there are words or phrases you stumble over or have to think twice about, cut them and replace with a more natural expression.
I also relied too heavily on pre-written speeches transferred to cue cards, so I made sure I put in something to break it up. I don't know what suits your topic, but I had an anecdote that I had scripted meticulously, but wrote it in colloquial language so that I could memorise it and then make it seem like improv.
An age-old solution is to get some friends in your class stationed in different corners of the rom so that you can look between the two/ three of them. Even if you don't know anyone too well, if any of the other guys are feeling similarly nervous, arrange with them to be each other's eye contact buddies.
As Anthony said, knowing your material inside out is the most important part. If you are utilising the cue cards, put a couple of asterisks to remind you to look up. Do this while you're practicing aloud and it'll become almost subconscious.
Worst case scenario you'll get below average marks for the "presentation" part, then you can rely on content marks to get you through this SAC, and earn back marks throughout the year. The oral is usually only worth 10% of Unit 3, so a mediocre mark won't hurt you too much.
I never found out the exact score for my oral but it wasn't spectacular. In fact I pretty much botched the SAC after that as well. But it gave me incentive to ace the next few. Worked out alright for me
You'll be fine!
Or seek asylum. Whatever floats your boat... sorry poor choice of words..