Question: Prior to the Flood, was the environment like that of a hyperbolic chamber which increased oxygen levels and created larger than usual plant and animal life?
Answer: Genesis 1:6-9 says, "Then God said, "Let there be an expanse in the midst of the waters, and let it separate the waters from the waters." God made the expanse, and separated the waters which were below the expanse from the waters which were above the expanse; and it was so. God called the expanse heaven. And there was evening and there was morning, a second day..."
It had been theorized from this that there was a layer of water some distance out from the earth that surrounded the earth. It is theorized that this canopy would create a greenhouse and/or hyperbaric chamber environment. If this was the case, it would be ideal for plant life and increase blood-oxygen levels in animals. The pressure would also help animals with very large lungs like T-Rex to breathe. Many Creationists today are questioning this theory.
See the following page at Answers In Genesis for articles on this subject: http://www.answersingenesis.org/articles/2009/09/25/feedback-collapse-canopy-model