Here in Central Oregon, we have a few lakes that have Lava Tubes in them where water drains from the lake.  Here is a great article/video from one of our local papers that shows how impressive one of these lava tubes are.  The water level at Lost Lake is quite low this year, making the lava tube visible.  Check this out:

http://www.bendbulletin.com/newsroomstafflist/3095112-151/lost-lake-shrinking-down-a-hole#.VTutp0–bqk.facebook