All myriad dharmas are but a single bubble in the great ocean of tathāgatagarbha

The Śūraṅgama Sūtra: 譬如澄清百千大海弃之，唯认一浮沤体，目为全潮，穷尽瀛渤。

The great ocean is a metaphor for the tathāgatagarbha, while the floating bubble, the seas and gulfs, and the foam are metaphors for the myriad dharmas—all the myriad dharmas are but a single bubble in the great ocean of the tathāgatagarbha. The Buddha is telling us not to take any single dharma among the five aggregates and eighteen realms as the true tathāgatagarbha, or as the self.

A body of the five aggregates is just one bubble; it is not the whole of the self. Do not let a single five-aggregate body blind your eyes so that you fail to see the entire great ocean of the tathāgatagarbha. All the dharmas within the great ocean of the tathāgatagarbha belong to oneself—not merely the present five-aggregate body and five-aggregate world, not merely the present wealth, sensuality, fame, food, and sleep, not merely the present world of the five desires. Therefore our vision must be broadened, so that we can see all the past lives and ages within the tathāgatagarbha, through kalpas and generations, all the way until the attainment of buddhahood and the worlds thereafter. Yet all these worlds are nothing more than bubbles one by one within the tathāgatagarbha, and nothing worth grasping. As long as we have grasped the tathāgatagarbha, it is as if we possessed the entire ocean—so why still care about a single bubble of the five aggregates?

In cultivating the Buddha's Dharma, one must grasp the essentials: take up the tathāgatagarbha as the guiding rope, and take hold of the myriad dharmas as the collar. When the rope is raised, the meshes open—so long as the tathāgatagarbha is kept in mind, one can see all the myriad dharmas, gathering the hundred rivers back into the great ocean. But if one takes the five-aggregate body as the self and as real, it will be like a single leaf blocking the eye, unable to see the vast expanse of heaven and earth.