If your idea of a great vacation means being near the water, make a beeline for Nonnenwerth. Whatever you choose to do here, you're unlikely to tire of those lovely views.
If you're heading to Nonnenwerth in Remagen, make sure you leave time to check out some other sights too. After you've covered off this water-surrounded land mass, Dragon's Rock is within easy reach and will keep you on the move for a while longer.