Coccolithophore

The arrangement of coccolithophores are as spherical cells about 15-100 micrometres across, enclosed by calcareous plates, coccoliths, about 2-25 micrometres across. Coccolithophores that are alive today have two brown pigment chloroplasts in their cell with the nucleus located between them. The pigments are home to the chlorophyll which carry out photosynthesis. In order to obtain the sunlight needed for photosynthesis, coccolithophores live near the surface of the ocean. Although they have the capability to swim, coccolithophores dominant mode of transport is drifting with ocean current and circulation patterns. However, they may maneuver individually to remain in the euphotic zone during times of extremely favorable conditions.

I can't image how they manage to "maneuver" with that structure.  A satellite photo shows them blooming.