The definition of swash is a geographic term for the turbulent wave of water that washes up onto the beach after an incoming wave has broken. I have often seen these but referred to them as foam. Now I know the technical term is Swash.
The action of the swash moves materials up and down the beach which results in cross-shore sediment exchange.
There are two stages of the swash. The first is referred to as uprush (or shore flow). The other is backwash (off shore flow).
Construction of manmade seawalls is a common tool used to protect beach property.
Now You and I Know. --RoadDog