We sprinted from Das Boot to the wet part of The Subway with our wetsuits on. This proved to be an excellent strategy. There is more water in The Subway than I've ever seen (over the past 7 years), and it is chilly. The weather only warmed up to 75-80 degrees, so those that we encountered without wetsuits were freezing their butts off.
Steph and I wore headlamps after reading that Das Boot is so dark in places that you might not be able to see. This is decidedly NOT TRUE. There are places where it is dim, but there is easily enough light to navigate with.
FWIW, you can swim underneath the jammed log in Keyhole falls. It is a tight fit, but all four of us did it. A couple of photos are provided below.
I've seen a bunch of photos of people rapping into The Subway.
This might be the most disturbing one.