Warning: don't attempt this hike without reading Phil Arnot's book Point Reyes: Secret Places & Magic Moments.
Here is the original announcement for the hike, and here are some photos.
We started from the Bear Valley Visitor's Center and hiked out to Arch Rock with me worrying that the 15 foot swells reported by offshore buoys meant that the unusually low tide wouldn't be enough to keep the waves out of Miller Cave (which determine whether I needed to alter the route to something less interesting). But when I saw the surf from Arch Rock, I decided they were low enough to attempt the cave (much less than 15 feet, presumably in part because they bent around Point Reyes and in part because the waves diminished sooner than forecast). So we hiked northwest to the Kelham beach trail to take the easy way down to the beach and to see Kelham Beach Cascade. We headed southeast along the shore for the interesting part of the hike.
Surprise falls surprised me by being dry in spite of what seemed to be decent rainfall around most of the area in the prior 48 hours (the rain must have mostly missed the area we hiked in). When we passed under Arch Rock, the stream crossing under the arch was easier than expected due to the low water in the stream. We continued a little further and had a late lunch on a nice warm rock ledge at the entrance to Miller Cave. When we arrived at an hour before low tide, the ocean was just about to drop low enough to leave the cave as accessible as it gets (i.e. the water was just barely low enough, whereas with normal surf, we should have had more like a foot to spare).
That's where the hard part began. The next 100 or 200 yards took 35 minutes. The cave entrance was mostly a tidal pool, with only narrow seaweed covered footholds along one nearly vertical wall. There were a few steps where the best handhold I could find consisted of shoulder-level barnacles. Troy bypassed those steps by jumping across the tidal pool (I wasn't willing to attempt that because the landing looked a bit awkward). Near the end of the pool we had to step in a few inches of water with one foot. Then the rest of the cave was pretty easy, and seemed like a fairly typical cave except that it was nearly U-shaped and that we went through it to get around a cliff.
Once out the far end of it, we traversed a seaweed covered rock face sloped at 40 degrees or less for about 30 feet (slipping here would have left us in 1 to 2 foot deep water, unlike the prior tidal pool where we didn't see any bottom). We carefully climbed up to a dry part of the rock. We passed under an arch and reached what I thought was the end of the hard part. The next 50+ feet involved traversing a rock face about 10 feet above the water on a slope of 70 to 80 degrees with many dry, firm footholds and handholds 2 or 3 inches wide. Despite the much reduced risk of slipping, one experienced hiker was less comfortable here with the increased harm that would result from slipping. He jumped into the deep tidal pool below and swam to the rocky beach at the end of the hard section.
The next mile and a half of shoreline was increasingly easy. We passed through a massive arch called the Temple, and I think two other less memorable arches. Horsetail Falls had very little water in it. I felt a bit cheated because Phantom Falls was dry - at 200+ feet, it must be the tallest waterfall anywhere near the bay area.
After reaching Wildcat, we returned via 6+ miles of ordinary trails, with the last hour being primarily by moonlight. I had hoped to finish by 6pm, but we ended up finishing at 6:48. Given the choice of low tides, it's hard to arrange this hike to finish any earlier without risking the tide being not low enough or having to start before dawn.