Acantharians are one of the four types of large amoebae that occur in marine open waters. Their fragile skeletons are made of a single crystal of strontium sulfate that quickly dissolves in the ocean water after the cell dies
 The bioluminescent, Pyrocystis lunula is a crescent or half-moon shaped dinoflagellate species that belongs to the oceanic plankton of tropical and subtropical seas. It is a single-celled alga (round nucleus) and reproduces asexually.
The Oarfish is a rare, solitary, and giant denizen of the ocean depths (arguably larger than a Whale Shark. (The as opposed to the Whale Shark, in the Guinness Book of World Records.)) and is a filter feeder, comfortable cruising at depths of 200 m.
Diatoms have cell walls called frustules that contain opaline silica and fine pores. The tiny pores in the frustules make them a useful filtering material for a wide range of industrial products, including beer and jet fuel.
20 eye-opening microscopic images from the Olympus BioScapes Competition