One thing, so in this book Optimus will be like in his twenties unless you want him to be a different age.Ya, he isn't old-age Optimus lol Also, this is short, sorry..

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No one's Pov

Optimus was frantically searching for a way to get Y/N back and out of the water.He knew that it wouldn't take long for her to freeze, so he turned to Earth's medical officers, in his holoform."Please do something, I'm unable to help her myself." He said with worry and sadness shrouded in his voice."We're working as fast as we can, Sir.You need to relax, she'll be okay." The female was tying a rope around he waist and had a long pole in her hand whilst consoling the Prime before he began pacing.

Optimus wasn't so sure that Y/N was going to make it out of this alright.And if she didn't..Her death would be his fault.

He didn't want that to happen.He didn't want her to lose her life like that, it wasn't right.

Quickly, three officers scaled the hill going down towards the lake.Each having a rope tied tightly around them so they wouldn't fall just as Y/N had.
Once onto the ice they had someone in a jumper type swimsuit dive into the water to retrieve the young girl.

Reader's Pov

I was going in and out of consciousness for what seemed like forever.I knew I was going to die, and it saddened me to think of all the people I was leaving behind.I hoped Optimus wouldn't blame himself for my dying.

I barely flinched when I heard a faint splash and a dim light could be seen above me.I could make out the shape of a person swimming down, I felt a wave of relief when they grabbed me and began pulling us both to the surface.

As soon as the air hit my body I realized how cold I was.Thankfully, I was rushed right to hospital and treated for hypothermia.After hours of recovery someone opened the door to my room.

Optimus rushed in and engulfed me in a lopsided hug because I was half laying down on the bed.

"Y/N, I apologize for everything that happened.I was so worried, are you feeling better?" He looked me over, seeing if I had any wounds."You don't have to apologize, Optimus.I know you couldn't control it," I smiled slightly."I am feeling better, so you have no need to worry." I said as he held my shoulders, staring into my eyes he said, "I'm so glad you're okay.I don't know what I would have done had anything permanently bad happened.." He looked like he would burst out into tears any second now."Hm?" I asked in slight confusion, clearly not getting the hint."Y/N, I love you." He hugged me again whilst my eyes widened and I processed what he said.I laughed a little and cried tears of happiness."I love you too, Optimus." I hugged him as well.

A/N
This might not be as good (I think I said this before) as my other one shots because I'm not used to writing about Optimus loving someone.Heh, hope you guys liked it!