To create a place that looks as if you just went diving, paint blue walls, add coral reefs and deep sea fish, and feature underwater . If you don’t want so much aqua in your room, you could have a neutral wall and then decorate with island decor to show off your underwater, deep blue sea and create a magical under-the-sea place. Exhibiting sea life is a perfect way to create, design an underwater themed interior and highlight the natural beauty of the deep blue sea.