I took this on honeymoon last year. I'd taken a few shots up until this, our last day. All of a sudden, further up the river bank, the sky looked as though it was about to catch on fire.
I ran down the bank, calling to my new wife "I've just gotta get this."
I used a high ISO in order to freeze the boat and an ND2 to keep the sky as my eye saw it.
I don't know why, but the large version doesn't look as good here as it does on my computer - the colours aren't as rich or deep in texture.