Squat

Squat is the bodily sinkage and change of trim a vessel experiences when making way through shallow or confined water, caused by the increased return flow of water under the hull lowering the pressure beneath it. It grows roughly with the square of speed and is more severe at high block coefficient and low water depth to draft ratio. In open shallow water a full-form ship typically squats by the bow; in a narrow channel the effect is amplified by blockage. Practical estimates use Barrass formulas, and the only reliable mitigation is to reduce speed.