This bottom of the tank cake is a 1 layer sheet cake. It looks like an ocean scene cake as well. With buttercreme icing,I used Wilton sky blue icing color for the water. I used 2 pks of nerds for the gravel, one of purple and pink and one yellow and red and mixed it. I went to a dollar store and found these fish, they were called fish on a stick and used the star tip to do a border around the bottom.
And the leaf tip for the plants, and used leaf green and juniper green for the icing colors. Very simple and cute.