Just How Do You Live in Water?
1. Seals' slippery, streamlined-hydrodynamic-bodies and flippers make them good swimmers. 2. Wave your hand under water, and someone will feel it. Lateral lines on fish help them detect movement at a distance.
Sea organisms need special adaptations for life in water because:

  • There's a lot less dissolved oxygen in water.

  • Food gets scarce once you leave the continental shelves.

  • As you go deeper, pressure increases.

  • Water is denser and more viscous than air. It supports weight better but it's more difficult to move through because it's stiffer.

  • As light travels downwards in water, different colors (wavelengths) are absorbed at different depths. Below 2,000 feet, the ocean is completely dark.
  
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