In the center of the page, the mighty mosasaurus takes the lead with its mouth slightly open, revealing its unique prehistoric teeth. Its long, muscular body stretches across the water, flanked by several smaller sea turtles that are paddling along beside it. You can see the detailed patterns on the turtles' shells and their gentle expressions.

A large school of fish darts around the background, adding movement to the scene. Near the bottom, various underwater plants and seaweed sway in the current. Above them all, gentle waves ripple at the surface of the water, showing just how deep these ancient animals have dived into the prehistoric depths.

Since the mosasaurus is a marine reptile, you might choose deep greens, blues, or even a sandy grey for its skin. Using a darker shade on its back and a lighter color on its belly can help it look more three-dimensional. For the sea turtles, try using earthy browns and olives for their shells, perhaps adding a few spots of bright yellow or orange for a pop of color.

The school of fish is a great chance to use bright, shimmering colors like silver, neon yellow, or vibrant purple to make them stand out against the blue water. You can create a beautiful gradient in the background by coloring the water near the surface a light cyan and making it a darker navy blue as you get closer to the ocean floor.