Marine flatworm (Pseudoceros sp.). This invertebrate is found associated with coral reefs in the tropical waters of the Indo-Pacific region. It has a brightly-coloured, flattened body and moves by beating its many hair-like cilia (not seen) or by undulations of its body. It uses a long retractable tube to catch its small invertebrate prey. Photographed off Derawan Islands, East Kalimantan, Indonesia.