Alexander racked his brain for some time trying to estimate just how deep the water under him really was.
And it was sorely due to this lack of knowledge that he was hesitating about jumping.
If it was a modern port, there would not have been any need to do such a thing because all harbors there were deep water ports- the depth would be tens of feet deep, if not more.
But here, in this time period, due to the lightweight of freight, harbors could be placed almost anywhere and so many times they tended to be placed on the shallows.
How shallow you ask?
Well, there were examples where Alexander had personally seen where the men literally waded to their ships from the harbor.
Meaning it could be as shallow as a meter.