Return flow of the water down the beach is called backwash, which is commonly called undertow when the pull is strong.

水流顺着海滩回流到海洋中被称为回流，如果推力很大的话，通常被称为退浪。

And I don't see a way to return blood flow to the brain.

我不知道怎么让血液流回大脑。