A sounding puzzle

Cartograph

Chart every cell of the channel before first light. Move the lead, then drop it to sound the 3×3 patch around it. Landing on a shoal fouls the line and costs time. Probe a cell to read its depth first, and when a squall band flashes, park the lead inside it to shelter your chart.

WASD / arrows move · Space drop lead · P probe · M sound · Esc pause · or tap the chart