How Deep is the Sea?

Extract

Because tankers are increasing in size some thought has lately been given to reducing the underkeel clearance in order to make more economic use of available water. But the problem is being stated in unnecessarily narrow terms by placing too much emphasis on tanker draught. A lot more cargo is still being carried in moderate tonnage vessels, which would show a sizeable economic benefit from a reduction in their under-keel clearance in many areas where tankers would not venture.