An aquatic microscopic eukaryote floats passively with plankton and possesses a wall made of two thin, overlapping silic
The organism is a diatom. Diatoms have two overlapping silica-containing wall layers and form part of the plankton. Their accumulated, indestructible wall deposits form diatomaceous earth.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Protista - Chrysophytes and Dinoflagellates