Final answer:
Dissolved oxygen is the form of oxygen that supports marine life, it is found in water bodies such as oceans and is crucial for the respiration of aquatic organisms.
Step-by-step explanation:
The oxygen which supports marine life comes in the form of dissolved oxygen. This is because oxygen is only slightly soluble in water but its solubility is critical for the survival of many aquatic organisms. In marine environments, water near the surface tends to have more dissolved oxygen than the deeper parts, partly because surface water can absorb oxygen from the air above it. Furthermore, the structure of the water molecule allows it to easily dissolve substances, which is essential for sustaining life on Earth. Organisms such as fish respire by using the dissolved oxygen in the water, and plants are able to absorb dissolved nutrients that are also available due to water's solubility capabilities.