I'm going to start this with a serious warning about Eagle Falls. It can be extremely dangerous and if you decide to swim, please wear a life jacket and use your best caution. Nature can be lethal, sometimes where we find the most beauty.
That said, holy smokes! Eagle Falls is absolutely one if the best swimming holes in the state. It's absolutely stunning. And you don't need to swim to enjoy it. I bring my hammock and a small barbecue and a cooler and just lounge all day! It's the best!
How to get there: It's easy! You can use your GPS like a normal human being or you can wing it. Live a little, would ya? Take Highway 2 East, like you're on your way to Leavenworth. You pass through the tiny town of Index, keep going for about 4 miles. Keep your eyes out for Milepost 39, you'll see a parking turnout on the South side. Park! Cross the street, see the signs that are warning of the waterfall and the extreme danger, take heed. Now hop over the railing and follow the path down to the Skykomish River and breath in the absolute Heaven before your eyes.