No injuries except some scrapes/bruises. I ‘m putting my own accident in here so that this hazard can be reported. This was on an ASCI promoted release (releases are first sunday of each summer month, at least this year) Experience class 4-lower 5. Other than this hazard, this river at this level was well within my skill level for the playboat used. The hazard is using the right breakout on the lowhead dam has the possiblity of pulling you under behind the dam. If you do not achieve enough speed or angle on the seam line that arcs around the lowhead, then you can be pulled behind the curtain in front of the dam. This is what happened to me. I got flipped on the seam line and rolled up pretty quickly and found myself in the cave. The cave is large enough to fit and roll up into. However, I was not able to escape without bailing out of my boat. I did swim out relatively easy, but that may have been good luck.I don’t other names in particular, but I think everyone that was there that day got the message. Some people were on the bridge above, and they may also submit a report if they know about this resource.