Her case probably would have no evidence for negligence. Sure there were no signs posted, however in a civil case like this the burden of proof requires that all evidence be on the 'balance of probabilities'.
This would mean that if there were signs would she have paid heed to them, or ignored them. If the later it wouldn't matter, she wouldn't be able to sue. If it was the former however, she could.
I for one doubt it could be seen or conveyed that she would have paid attention to the signs for many reasons:
- it was a midnight swim. Who goes for a midnight swim sober? There was probably alcohol involved, thus dimming her common sense - signs would not have been the first thing on her mind.
- it was a midnight swim. Unless glow in the dark the signs would not have been noticeable so she wouldn't have paid attention to them. She couldn't expect them to instal indvidual sign lights because it would not be probable to assume anyone would be swimming at 12am.
- it was a private swimming pool. I have never seen a private pool with signs. She should have taken heed of this fact and realised it wasn't the same as a public pool, water depth would not be the same.
- even if there had been a sign would the accident have occured? She may have been warned, she may have taken a little more precautions, but who is to say she wouldn't have landed the way she did?
It wouldn't stand up in court. Some Lord said about Boxers - "one who is willing cannot be hurt", meaning, in a boxing match both take part knowing there can be injuries, no one can sue the other if they occur. With events like swimming it is probable there are injuries that could occur, if you willingly go ahead, do not expect compensation should liability arise.
However, if it can be proven she could sue the NHS Trust I would. If there negligent care caused me added injuries or heightened my already apparent injuries I would have compensation to pay for my life-long care.