Headed to big bend soon…

Which canyon would be the best for a half day canoeing?

Santa Elena Canyon is where we used to canoe the most years back. Put in at Lajitas. It has the highest cliffs.

Have not been there in a very long time though.

Bouquillas Canyon with lunch at Jose Falcon's.

Definitely check the flows

When we were there last month we did a half day float starting in the state park but water was very low everywhere. Check with the outfitters

With the water low - was it worth it?

Call Far Flung and ask them. They can also help with shuttling if you need that.

If you're only interested in taking up a half day. The easiest and probably best option would be to put in at the mouth of the Santa Elena canyon, paddle upstream stream a few hours then paddle back. This option let you control the time and eliminates any time wasted in shuttles and complicated logistics. Best bang for your buck in terms of time. I believe several outfitters offer a canoe drop off and pickup for this exact type half day rental. This trip would put you right in the heart of some of the deepest canyon walls the park has to offer.
However still the call outfitters as current flows will dictate what will work with your timeline and interests. They maybe be able to recommend or put together something else that matches what you want to do.