knocking/juddering after driving in storm

Hi we have got a discovery 3 which I drove in a storm last night. I had to pass through 3 small floods to get home, I crawled through in 2nd in the middle of the road avoiding the sides. When driving normal, there was water at the sides of the road but this would have only reached my wheels, not the underneath of the car. Anyhow, I stopped but kept the engine running to pick my son up then a few seconds after pulling away the car felt like it was 'juddering' and labouring so I pulled over. Every time I tried to move forward, it sounded like a knock on the passenger side, mid to back end. After 10 mins or so, I tried again and the car drove 2 miles home absolutely fine. Hubby got in it when I got home and it started knocking again - to him, it sounded similar as when the prop shaft started to go last year (this was fixed with genuine parts by landrover). Got in it this morning and its doing the same sound so it's off to land rover we go again. Anyone any ideas on what it could be? I would have thought it was going through water, however going through at the same speed and in the same way that a normal car (as in that which isn't known for off road), I wouldn't expect it to be. Thanks

Is it a manual or automatic?

It's a 2.7 diesel manual

Does it still do it when out of gear and rolling?

Sounds that despite your driving water has managed to get a sensor. It's doing something to the drive train. Not discovery expert. Diff locking mechanism, anti-skid sensors etc. I'd see how it goes for another day before incurring LR dealer costs; they are are a rip off. If you avoid deep water and see if it dries out first?