The ocean stands for God, the sole substance, and individual beings are like waves - which are modes of the sea. Each wave has its own shape that it holds for a certain time, but the wave is not separate from the sea and cannot be conceived to exist independently of it. Of course, this is only a metaphor; unlike an infinite God, an ocean has boundaries, and moreover the image of the sea represents God only in the attributes of extension. But maybe we can also imagine the mind of God - that is to say, the infinite totality of thinking - as like the sea, and the thoughts of finite beings as like waves that arise and then pass away.