Traditionally risks for delays in getting into the berth were apportioned between the owner and the charterer in a way that all risk as to navigation, weather and alike were rested upon the owner and those as to congestion in the port or non-availability of the berth were on the charterer since it is they who determine the ports of loading and discharge, but some of these liabilities are usually transferred back to another party by way of exceptions.
In EL Oldendorff & Co GMBH v Tradax Export SA (The Johanna Oldendorf),  AC 479 by Lord Diplock at p556-557:
The adventure contemplated by a voyage charter involves four successive stages. They are:
1. In all four of these stages acts of performance by the ship owner are called for; in the two voyage stages acts of performance by him alone.
2. The loading operation, viz. the delivery of the cargo to the vessel at the place of loading and its stowage on board.
3. The carrying voyage, viz. the voyage of the vessel to the place specified in the charter party as the place of delivery.
4. The discharging operation, viz. the delivery of the cargo from the vessel at the place specified in the charter party as the place of discharge and its receipt there by the charterer or other consignee.
The standard forms of charterparty do not usually include an exception clause for delay caused by the inability of the vessel ot load or to discharge her cargo because of congestion at the place, whether berth or dock or port, specified in the charterparty as the place of loading or discharge. So any loss due to delay from this cause falls on the party who is thereby prevented from doing timeously what, by the terms of the charterparty, he had undertaken the primary obligation to secure was done.
Herein lies the importance of the four stages into which the adventure is divided. Each must be completed before the next can begin. So until the vessel has reached the specified place of loading on the loading voyage or the specified place of discharge on the carrying voyage, the contractual obligation to bring the vessel there lies on the shipowner alone; and any loss occasioned by delay in doing so falls on him.