Hundreds of thousands of spider crabs blanket the waters off Australia.

According to the BBC, spider crabs migrate to the southern waters of Australia annually when the seawater cools down.

Oceanographer Sheree Marris captured images of spider crabs in Port Phillip Bay to draw attention to the diverse marine life in the area.

The exact reason for spider crabs' large grouping behavior is unclear, but scientists speculate it's most likely related to molting. When spider crabs shed their hard outer shells to grow, they become easy prey for predators like cormorants and stingrays. Gathering in large numbers helps increase the safety of the entire group.

• The unique practice of raising freshwater crabs that feed on rice flowers in Nghe An.
• Unique method of catching crabs in burrows using bamboo in Nghe An, the "rice-growing homeland".
• The road lies below sea level in Khanh Hoa.
• Growing vegetables using seawater.