Why can't I wade in the pool?

For reasons of safety.  The pool has many lights and sharp fountain heads that could injure visitors. 

How are the states arranged?

Much like a formal dinner table. The host or guest of honor is at the center, in this case the field of stars.  To the right of the place of honor would be the next most important, in this case the first state Delaware. To the left of the center would be the third, in this case the second state Pennsylvania.  Then it simply goes back and forth around the circle.