At this time people were beginning to live in villages. That means farmers and fishermen.
Not entirely true afaik. It's 7500 BP when the boundaries we now have were made, that's 5500 BC (roughly). People started to live in villages in Holland in about 6000 BP. But yeah they had hunting camps. But they could easely see the water come and back off.
Maybe you heard about the story about Mammoths and Wooly Rhino's drowning into the sea on Doggers bank, well that isn't true. Firstly because they were extinct. Secondly because Doggersbank was already a muddy, wetland when it became separated.

And about the trees, they can't live in salt water

The Jewish Flood I explain via the Black Sea incident. That was a rapid rise in water and likely many people died because of this.
Another possible culprit would be when the Atlantic broke through to the Med. However there doesn't appear to have been much land gobbled up by the water there.
I read about another theory for this flood.
One of the Greek island would have had a volcano, that errupted and caused a tsunami, and that flooded most of Egypt and Isreal as we know it now.

They also made a different theory about Moses with this.
Before the flood comes the water pulls back, at that point Moses and his bunch cross the sea and when the Egyptians are there the Tsunami comes.