Pics from the past...

taken during one of my numerous descents in the mid-1990s into Papoose Cave in Idaho, ranked as one of the deepest caves in North America.  Here's an image showing fellow caver TM at the top of the first waterfall pitch, about to begin his rappel:

This challenging, cold, wet and deep cave is developed in the steeply dipping Martin Bridge Limestone (Triassic) in north-central Idaho, and the active cave stream has carved narrow but high "canyon" passages:

Some grottoes are nicely decorated with white speleothems, these in the "Bluewater Extension" portion of the several-mile long system:

Water levels can vary tremendously from one year to the next depending on surface runoff into the cave, and flotation is required in some sections in order to traverse the water-flooded passages:

Here's a link to the Idaho Geological Survey publication Speleography of Papoose Cave, Idaho (warning: 25 MB .pdf file).