A semi-submersible gas burner assembly for a fire-on-water feature, the assembly including a tubular void former having nominal waterline disposed between proximal and distal ends and a separable lid engaging the distal end. The lid includes inner and outer peripheral skirts projecting toward and past the waterline, respectively. At least one gas manifold arm extends through and outward from the tubular void former, and includes a gas port disposed proximate the sidewall. The sidewall at the distal end includes a communicating aperture which fluidly interconnects the interior of the tubular void former with a flame retention chamber defined by the sidewall, the lid, the inner peripheral skirt of the lid, and the nominal waterline.