An inlet channel 1.7 meters above the bottom level of the 4.26 meter deep tank allowed excess water to escape. Other inlets prevented siltation of the tanks and erosion of the banks. After a ship would have unloaded its cargo, the gates would have opened and allowed it to return to the Arabian sea waters in the Gulf of Combay.
Archaeological finds from the excavations testify to trade with ancient Egypt and Mespotamia. The hydraulic knowledge of the ancient Harappans can be judged by the fact that boats could dock at Lothal in the 1850's. In 1942 timber was brought from Baruch to nearby Sagarwala. It is said that then the dockyard could hold 30 ships of 60 tons each or 60 ships of 30 tons each. This would be comparable to the modern docks at Vishakapatnam.