Welcome to the forum! Pint is a very cute name for your turtle.
A filter is definitely recommended from the start unless you want to be doing partial water changes every day to keep the water clean enough for your turt. As for the water level - how many gallons is your tank? He definitely needs deeper water than only an inch. Turtles are natural swimmers, absolutely, just make sure you have a few plants for him to rest on especially since he's so young. It's great if you fill you tank as high as it will go, but without the turtle being able to climb out of the top (and they're exceptional climbers!)
What I did with my babies when I got them was fill the tank up about halfway, and gradually added water every week until it was as full as it would go without them being able to escape. I know they would have been fine without me doing that, but worried old me couldn't help it.
Your best bet is to read all of the sections on the main website:
http://www.redearslider.com to learn all you need to know about general turtle care. If you have any further questions after that please don't hesitate to ask them. Glad to have you and Pint on the boards!!
