It's interesting, though, how certain themes present themselves. The three you chose - and the Shakespeare as well - are about ephemerality. They put the reader apart from the beach, from the ocean, and make it something different from normal experience. The last one (Mulla Mulla Beach) goes a little further by separating the author from the people he observes. There's an "otherness" to it. You know what would be interesting to me? A comparison with poems about the desert. I suspect you will find many similar themes, but also stark contrasts. There's something forgiving about a beach that a desert will never be. And while I recognize that there aren't many deserts within driving distance of Delaware, a sojourn might be interesting to you.
Arcosanti's a trip. I stayed overnight there. It's crazy cheap. If the Mos Eisley Spaceport were in a post-apocalyptic future written by Douglas Coupland, it'd be Arcosanti. This book is legit outsider art. Paolo Solari is probably insane, but since he's an insane architect rather than an insane cult leader he gets a bye. It's kinda funny - one of the few things he ever did for money was design a foundry building. It was there he fell in love with slip-cast concrete. So now everything is slip-cast concrete. he's even got a foundry. And hey - $300 a week to run off and join the Lost Boys while eating hippie chow. Just pick your season carefully.