Was Seth Adams son still alive during the Noah's Ark incident?

NO. It is estimated, through Bible chronology, that Adam was created in 4026 BC. He lived for 930 years and died in 3096 BC. He lived to see Noah's father Lamech of the ninth generation. (I Chronicles 1:1-4) but died 726 years before the flood, which took place in 2370 BC. Adam died, just as God had said.-Genesis 5:5