How do some marine invertebrates and fish live under such high pressures and do they have any special enzymes?

Following are the main adaptations:-

• Lung-like swim bladders which help in maintaining buoyancy. Collapse of the swim bladders is prevented by maintaining internal gas pressure equivalent to that of outside.
• Lungs are compressible (beaked whale) forcing the gases into the blood from where these gases can be released outside.
• Presence of trimethylamine oxide (TMAO) that prevents the distortion and compression of proteins.
• No nitrogen absorption: This prevents the development of nitrogen narcosis and decompression signals.