A giant barrel sponge (Xestospongia testudinaria) on a coral reef wall of Menjangan, Bali. These sponges can live for over 2,000 years, grow up to 6 feet wide, and filter vast volumes of seawater, greatly improving water quality, and also provide shelter and habitat for a variety of small fish, shrimp, and other invertebrates.

Barrel sponges are particularly susceptible to human impacts of pollution, reef destruction and climate change so that this vertical shot featuring a barrel sponge against the blue surface light, reinforces for me the importance of marine protected areas.