The titled work in the abstract creatures series, and the most encyclopedic of Sidney's imaginary zoological paintings. The composition reads like a field guide to a world that does not exist — or that exists only at scales invisible to the naked eye, or at depths no light has reached, or in the imagination of someone who has spent long hours with both microscope slides and watercolor paper.
The surface is populated with creatures and forms of extraordinary variety: transparent bubble-like spheres containing miniature worlds, hairy centipede-like forms, spotted and banded worm shapes, creatures with fins and without, a fish rendered in clear orange-red at center right that is the most conventionally representational element in the work, a blue stingray at lower right that has the quality of a painted specimen, a hairy brown caterpillar at lower left that could be from a Victorian natural history illustration. Alongside these quasi-representational forms are purely abstract elements: pools of purple watercolor, spiraling orange marks, dotted lines, small circles.
The ground is the work's organizing principle: warm white at center, graduating to yellow-orange at the edges, with purple and blue passages creating a sense of water or atmosphere through which the creatures move. The upper border carries a parade of small spheres — circular forms in various colors arranged in a nearly horizontal line like a specimen row or a molecular diagram.
The title declares Sidney's intention: these are sea creatures, and the work is the first in a series. The biological specificity of some forms (the caterpillar, the fish, the stingray) suggests that Sidney was looking at natural history sources while making this work — then departing from observation into invention.