A great way to teach one-point perspective. Start with a central vanishing point. Add 'windows' down each side and a curved ceiling. Use blue ink to paint the 'water'.
Outline the edge of the windows and the ceiling. Use permanent markers to make a 'chess board' pattern on the floor. Once this is done, get the students to draw and colour their underwater creatures on a separate piece of paper (remind them to make them small enought to fit into their aquariums!). These can be cut out and glued on when finished.
As a final touch, we also added silhouettes of people walking down the aquarium 'hallway'.