Does anyone have experience logging velocity and/or discharge in underwater caves? I'd like to measure changes in discharge in underwater conduits as deep as 100 m as they reverse flow, such as occurs over a tidal cycle. ADVs seem to do a good job making point measurements of velocity, but they are expensive and require particles in the water and some springs are too clear. Many of the cheaper (<$15k) instruments have shallow depth ratings are the loggers are not designed to be placed underwater. If anyone has any suggestions, I'd be keen to hear(read) them.
Thanks,
Jason