I have seen small dinghies sailing incredibly close to anchored cargo ships and I fear that they don't understand the dangers they are facing. While it is never a good idea to sail right up next to a massive ship because items can fall off the deck and strike your tiny boat! Even worse are the dinghies that sail between the bow and anchor chain.
Right under the water lies the cargo ship's bulbous bow! These protrusions vary in size and length, some coming way forward of the waterline.
The winds around the bow are quite squirrely, adding complexity to a cramped area with little sea way. Adding to the confusing winds is the fact that your keel and rudder could strike the top of the submerged bulbous bow, causing damage to your boat and confusion to the crew.
Not all bulbous bows are the same, some are longer, some are shorter, but they all can lurk just below the water ahead of the ship!
While I do not recommend sailing close to a cargo ship, there are some clues as to how extensive the bulbous bow could be.
The sharper the bow, the longer the bulbous bow could be.
The blunter the bow, the shorter the bulbous bow could be.
The bulbous bow tends to be as far forward as the tip of the bow of the ship.
While you don't want to sail too closely to a ship (especially one that is moving), if you do find yourself right on the bow of a ship and feel a thud before you come in contact with his bulbous bow!