You know you've been looking for this skirt. The one where leggings are attached to it. here are some great examples. note: some of the skirt with leggings attached are longer then others.
Swim/Running Leggings with Skirt Attached Plus Size
Sporty Double Stripe Long Water Skirt/pants
Grey Swim Skirt With Leggings
Splash Down Denim Swim n' Sport Skirt