There are plenty of beaches all over the world, and no matter which one you go to, you're bound to see the following: kids, water, sand, and sea creatures. The setting of "maggie and milly and molly and may" is pretty universal in terms of its aquatic landscape. Sure, the names sound American, but you can go ahead and swap those names with any language of choice and the setting and themes will stay the same.
Most folks can't help but feel at least a little intrigued by the enduring quality of the ocean, which for many creates a soothing or reflective experience. And experience, not beach time, is really the whole point of this poem. The setting is what produces in the kids—and for us readers—that sense of finding yourself, of going out into the bounty of nature (in this case, filled with lazy starfish and bubbling crabs) for a chance to soak in that big picture of life, the universe, and everything.