Giant clams are large marine bivalve mollusks found in warm, shallow waters of the Pacific Ocean and Indian Ocean. They can grow up to four feet in length and weigh over 500 pounds. These clams have colorful mantles that can be blue, green, or purple, which help them attract sunlight for photosynthesis. Giant clams are unique because they have a symbiotic relationship with zooxanthellae, tiny algae that live in their tissues. This relationship allows the clams to obtain energy from sunlight, while the clams provide the algae with nutrients. They play an important role in coral reef ecosystems by providing habitat and food for various marine species.