This is an unusual question. Nothing qualitative really happens upon its increase in density and this is quite a difficult thing to do: mere fluctuations in temperature and pressure (even immense changes) can shift water's density by as much as only 3%. Water is most dense between 4 and 5 degrees celsius. There is a drop in density below this (even when supercooling the water).
it gets denser
Salt water is denser than unsalted (fresh) water.
light rays bend away from normal as it passes from denser water to rarer air
the water goes into a cycle which means that the water gets hotter as it gets closer to the sea floor.
Most types of wood are not denser than water--they float in/on water. For the wood types that are denser than water, the explanation is that they contain molecules that are denser than water (e.g. resin) and the average distance between molecules is smaller.
The water gets cooler
when the water cools down it gets denser
What happens to the water molecule is when it is evaporated, it is being bounced around. Then, when the water molecules are rubbing together, that creates friction, and friction creates energy, that energy is the lightning. Next, when the cloud is collection water, it gets denser and denser, and when it is very heavy, the water just falls out because the cloud can't carry anymore.
they sink
it gets denser
I think it sinks toward the ocean floor.
Salt water is denser than unsalted (fresh) water.
Some of the sand will sink to the bottom of the water. There is no chemical reaction. However, some of the sand may go into suspension, making the water muddy. This is a physical change that can be reversed by filtering the muddy water.
It gets colder and denser - it is at its densest at about 4 degrees centigrade. If the water gets even colder then it will freeze and ice will form. As this happens the molecules actually move further apart (water ice is unusual in that the solid form of water is less dense than the liquid form - which is why ice floats).
By physical examining the milk and water, you can easily judge that milk is denser than water. As milk is denser, its molecules require more energy to gets excited and evaporate as compared to water.
It gets colder because the Sunlight heats the ocean and the deeper you go, the less penetrating the Sunlight is, therefore making the ocean water colder.
The boat will rise because salt water is denser than river water.