Two sailors are constantly sounding the water with a long bamboo rod, while another looks out for floating objects (trunks, trees) and informs the bridge of the depth by gesture: 3 fingers raised correspond to a water depth of 3 cubits, 3 fingers and thumb at right angles mean 3 and a half cubits, whole hand raised: 5 cubits, etc.

Two sailors are constantly sounding the water with a long bamboo rod, while another looks out for floating objects (trunks, trees) and informs the bridge of the depth by gesture: 3 fingers raised correspond to a water depth of 3 cubits, 3 fingers and thumb at right angles mean 3 and a half cubits, whole hand raised: 5 cubits, etc.