The composition, based on Edgar Degas's reconstruction of the salvaged fragments from Edouard Manet's The Execution of the Emperor Maximilian (1867-68; National Gallery, London), is constructed of four pieces of canvas mounted to a larger piece, first painted muted red. Once the fragments were in place, Johns began painting the areas around each fragment an earthy yellow, additionally outlining the fragment edges with thicker paint. Also visible in this image, seen most prominently in the upper gray layers, is the nature of the medium, encaustic, or bleached beeswax and pigment, which the artist mixes in his studio and can manipulate by melting and tooling after the paint initially cools on the surface. The drips and bubbles at the lower right are the result of this re-melting.

Johns created an outer border around the entire perimeter, accentuated by a thick charcoal line and underpainted bright blue. Here, all three underpainted colors—red, yellow and blue— are visible, as are subtle hues of gray, each nuanced to achieve specific effects. Instead of simple mixtures of black and white, Johns used a number of blacks along with white and, at times, complimentary colors to mix his various "grays." The thick brushstrokes on the left illustrate Johns's main reason for using the encaustic medium: it dries quickly and captures the nature of individual brushstrokes, allowing the artist to paint quickly in layers without interruption while leaving the underpaint and process visible. At the far right, small, diagonal, parallel striations in the paint are the result of dragging a texturing tool, likely a mezzotint rocker used in printmaking, across the hardened paint.

Near the Lagoon is part of Johns's Catenary series, a group of works featuring perfect curves created by a string suspended from two points. To set the curve, he impressed the cord into the paint and also layered strokes of gray encaustic over its edges. Once he had captured the cord's position, he pulled it out of its groove, sometimes leaving broken edges, sometimes pulling up the paint beneath where the cord had been. Often this process was repeated more than once along the same curve. To the left of the curve a piece of fabric has been pressed into the warm encaustic paint, leaving a wrinkled impression. At the far left, perfectly straight drips common throughout this work and others were created by running a bead of encaustic paint across the surface in a straight line.