What are the limitations of the respiratory system?

Having gills, or the ability of gills.

Explanation:

Our lungs can't filter out water and use the oxygen in the water, sadly.

And, we can't hold our breath for that long, compared to other mammals (the only way that we can hold our breath for a long time is if we breathe in pure oxygen).

well, you see. the answer to your question is quite simple. the thing that is big, powerful, and over 9,000 is your mom.