On the West coast of Kauai (Polihale, Barking Sands), the military has tested missile defense systems. I don't know the story behind the remains of the tank here, but it certainly makes a stark contrast with the raw beauty of the ocean.
The helicopter ride was a thrill! Picture Magnum P.I. with a one-point seatbelt and no doors! A guidebook we used says "going to Kauai and not taking a helicoptor tour is like going to the Sistine Chapel and not looking up." So we went. Here, you're looking East from the Na Pali coast. Ke'e Beach is in the foreground, and if you squinted, you could see the resort where we stayed. I've done a poor job capturing the blues in the water below -- it's actually quite a bit richer than what you see here.
We did a lot of exploring on Kauai, and on this day we found an abandoned car with some happy plants. The Northern part of the island is very green and lush. It gets about 80 inches of rain a year vs. the West coast, which only gets about 16. The wettest spot on earth is in the middle and gets about 450 inches a year!
Ke'e Beach is at The End of the Road on the North shore of Kauai, about two miles West of our resort. The snorkelling there is fantastic, as are the trails that lead into the Na Pali coast wilderness. It is very likely that if you see a sunset shot from Hawaii that includes coastline, it was taken from Ke'e Beach.