People of the Dawn
We will never know when the first people arrived in the Americas.

If they were dependent on coastal resources, then the evidence may be 100 miles out in the Gulf of Mexico and 400 feet below sea level. Finding it with our present technology would simply be impossible. But artifacts have been found that can be dated to around 13,000 years ago.
People Friendly Environments

Like the ancient critters, the first humans to discover the wonders of the Americas had environmental preferences. They required fresh drinking water, resources for gathering or hunting food, and a landscape which fell within a range of temperatures that their bodies and abilities could handle.

Some researchers believe that there was a corrider all around the Northern Pacific and the ice margins of the glaciers.

Evidence absolutely demonstrates that people arrived in Australia 40,000 years ago. There is a model from the Arabian Peninsula that may offer a possible alternative. Over time, people moved from the fertile areas into more difficult landscapes.

The map to the right is how I conjecture the Tampa Bay area may have looked 12,500 years ago. The Gulf of Mexico was at least 60 miles further out at that time.

If you were to live off the land, what should you do first?

Plant fiber is the most readily available resource. Nets, traps, and snares will secure a reliable food resouce when used correctly. Finding the stuff with which to make twine would be your first priority when moving into an area. Nets used in a healthy estuarine environment result in a variety of food resources.

The problem with hunting is that darts, spears, and throwing sticks (like a boomerang) require skill, endurance, an absolute familiarity with the creatures being hunted, and plenty of prey to hunt.

Therefore, I beleive that coastal areas were likely the best place for those first people to have lived because fishing would have sustained them.
We all come from a place of our own prejudices. That's reflected in our use of language. If I use the word primative, it often reflects an image of ignorant and savage people living in caves and using animal skins as clothing. Savagery is probably more common on the streets of our inner cities and halls of our corporations than it was in that ancient world.

I prefer the term primal. The primal people were as intelligent and resourceful as we are. They were beginning the technology that would lead to our modern world.

The map above gives some idea of how harsh Florida's interior may have been at certain periods in our prehistory. And yet, evidence of ancient people using it is fairly common.

Why would people make use of and adjust to such a challenging environment?

Were coastal populations swollen to their maximum capacity? Were there too many people living on the coast? Or did the breakdown of the glaciers stress the estuarine based economy? Did an inundation of cold, fresh water into the Gulf cause shellfish populations to die out? Were coastal tides suddenly absolutely unreliable?
We may never know the answer to these questions, but something drove those ancient people up the rivers to hunt in the interior.