A serene pencil drawing of a sea turtle gliding through water with light rays penetrating from above, rendered with fluid grace on pure white paper using graphite. Capture the turtle's streamlined form with careful attention to the shell's geometric scute patterns, each section showing individual texture and natural wear marks. The flippers should be drawn with proper anatomy showing the way they curve and flex during swimming motion. Render the turtle's ancient, wise face with expressive eyes and beak-like mouth with realistic detail. Show the underside of the shell (plastron) with its characteristic pattern. The water environment should be suggested through creative use of light and shadow - draw god rays or light beams penetrating from above using negative space and careful gradation, small fish schooling in the background rendered as simple silhouettes, and perhaps coral or rocky bottom elements below in softer focus. Include floating particles or plankton as small dots creating atmosphere. Use smooth blending techniques to create the fluid, underwater feeling while maintaining sharp detail on the turtle itself. This peaceful underwater scene should celebrate marine life with technical skill and environmental awareness.