Das Boot, an absolute Zion classic! Deep, dark, convoluted narrows, long swims, and a relatively easy approach, this one is a must do. "Standard" Das Boot is often done as an extension to the Subway. For a competent group, this only adds an hour or so to the regular Subway from the top route and is highly recommended, though you will need full wetsuits for Das Boot even in the hottest part of the summer. I would not recommend doing the standard Das Boot by itself. The approach and exit would take away quite a bit of the fun.

Wait! While standard Das Boot is a nice addition to the Subway, there is an alternate entry that makes Das Boot a fairly good day on its own. This is considered Upper Left Fork of Great West Canyon, or an extended Das Boot, and takes about 5-7 hours on its own, without adding the Subway. The extended version is by far my recommendation. It doesn't require a car shuttle, and gives plenty of time for enjoying the canyon without feeling pressed for time. The permit is also typically easier to get than a Subway permit.