That is the number one concern that none of us can realistically address until we get to the UK. We're going to treat our time there like she will definitely be swimming and completing the effort. But there is no guarantee that either of those things will happen. Success or failure is part of the story we will cover. And that will be the story told in the documentary.
If she doesn't swim at all, it would be virtually impossible for her (or us) to come back and attempt the swim again in 2019, in which case we would most certainly not be able to deliver a finished product for our estimated release date. Were that the case, we would work closely with Sarah to see what her plans & intentions are for a second attempt, and the timeframe in which it would happen.