I'm a water girl at heart. The sound of the ocean is music to me. It has many different variations of sound. Sometimes you'll hear the gentle lapping of the tiny ripples on the shore. Other days you'll hear huge waves crashing against the rocks.
Streams are nice, too.
The gentle sounds of a stream create a peaceful and intimate atmosphere. Water, in general, generates negative ions, which purify the air and make your workout more invigorating. You don't have to spend any money on equipment if you don't want to. Sometimes buying a few accessories helps to firm up your commitment to practice, though, and they make some of the poses easier. The most basic item is a yoga mat that provides a clean, non-slip surface for you to practice on.