Answer:
4. Three ways in which ocean water varies are salinity, temperature, and pressure.
5. The temperature of ocean water varies with the location and seasons.
6. Water temperature decreases as you move from the surface towards the ocean floor. This is because sunlight warms the surface water, but deeper water is much colder.
7. Scuba divers are prevented from going deeper than 40 meters below the surface due to the increased pressure at greater depths, which can be dangerous without proper training and equipment.
8. Ocean floor features such as trenches and mid-ocean ridges form through tectonic plate movements. When plates collide or separate, they can cause the ocean floor to be pushed up or down, creating these features. Trenches, for example, are formed when one tectonic plate is forced underneath another plate, causing a deep depression in the ocean floor. Mid-ocean ridges, on the other hand, are formed when plates move apart, allowing magma to rise to the surface and create new ocean floor.