Why is it more difficult to lift a wrecked boat from a muddy bottom than from a rocky one at the same diving depth?

The area of ​​contact with the bottom plays a special role here. When the boat is on the rocks, it is very easy to set it in motion, since the contact area is small. The opposite situation is with the muddy bottom. Almost the entire lower part of the boat is adjacent to the bottom. Raising a boat, for example, can be compared to picking up a telephone or some other object from a table. It is difficult for us to lift this object, we most often move it to the side or poke it under the bottom. We feel that the table (in our case, the bottom) does not let go of the object. The bottom still sucks the boat into itself.