Photosynthetic algae, which are comprised of a siliceous skeleton (frustule) and are found in almost every aquatic environment, including fresh and marine waters, soils, and any moist environment, are known as diatoms, etc.
Diatoms are used in forensic sciences to diagnose death by drowning.
Diatoms can synthesize their own because of photosynthetic pigments such as chlorophyll which can harness the sun's energy.