A couple of ideas which may or may not be new to your browsers.
Hot summer day, secluded site in the sand dunes on beach, wearing only swimwear. Make sure the coast is clear, take off the swimwear and sunbathe nude. When you're ready, slowly wank to ejaculation; I suggest lying in the dunes.I've done it, and it gives a good sense of freedom.
Secondly, same format, and although it may not be strictly for this site, if your female partner wears a bikini, she can slip off the bottom half and have open air sex. My girl likes this.