Final answer:
When river water flows into the ocean, it creates an estuarine environment where the density of ocean water, which is higher due to salt, allows sediments to settle. The density contrast also affects the buoyancy of floating objects such as ships, which are more submerged when loaded.
Step-by-step explanation:
When a river flows into the ocean, it encounters a vast body of water with different properties. One stark difference is the density of ocean water, which is higher than that of river water mainly due to the salt content in the ocean. As fresh river water mixes with the salty ocean water, it creates an estuarine environment where sediments like gravel, sand, and silt can settle if the current is slow, contributing to the formation of deltas. The density of a fluid is also a crucial factor in determining the buoyancy of objects; as the density of water increases, an object can float more easily. A ship, for example, will be more submerged when it is loaded due to the increased density of the loaded materials.