We have just been on Costa Mediterranea and had a restricted view cabin with balcony. Ours just had a lifeboat but the top of the lifeboat was the same height as the floor of the balcony so the view wasn't restricted at all. I am sure you will have a wonderful time as we did.
If you 'Google' costa atlantica deck plans, it will take you straight there. You should be able to work it out from there. Good Luck.
I havent have an obstructed view with Costa but have with Princess. The lifeboat took up a limited amount of our window. We didn't have a perfect view of the water but it certainly did not bother us a bit. The view that we had was still phenomenal!