Based on the wiki of the last two seasons, the leg with the second U-Turn has always ended with 4 teams left in the race, so I would expect it in this episode.
With it historically being Detour --> U-Turn --> Roadblock, the racers getting massaged, if it's the roadblock, don't look like they have very wet hair. Of course, that might not mean anything.
If Margie & Luke and Kisha & Jen continue feuding, then the U-Turn is the most likely weapon--via Jaime & Cara or, if they made a deal with them, Tammy & Victor--because I don't expect them to continue running into each other at clueboxes.
The only things that are throwing me off are the fact that it's dark out when Margie & Luke finish swimming. Since the massage and the swimming & diving are all indoors, daylight might not matter in this leg. How late does this leg go?
It's too bad I can't make out Cara's watch at the massage.
I don't know what it means, but Luke is only wearing a white t-shirt both in the taxi after swimming and at the massage.
If the Roadblock is just getting a massage, then a U-Turned team is not going to be able to make up much time at the Roadblock.
Since I didn't see anyone else guess it, if the swimming & diving are the Detour options, then I'm going to guess that the Detour is called "Sink" or "Swim."
About Tammy & Victor, if they weren't stuck between the two feuding teams in the last leg, they probably wouldn't have appeared at all in the previews.