Many people who survived the brunt of the wave died anyway when the wave sucked them so far out. The receding wave pulled anyone in the water hundreds of meters out to sea ... sort of like a rip tide except there's no way to escape it.
I've also been in rip tides and undertows. As teenagers, we actually sought them out but we also had extensive experience whereas the typical European tourist wouldn't. When dealing with a strong current, rip tide or undertow, don't panic and don't fight it are the carnidal rules of survival.
I would have been most frightened of the debris and of being crashed into stationary objects on the shore. On the outflow, I would have been less concerned with being swept out to sea than I would have of of coming in contact with all the debris... either on the initial surge or retreat.