The mind is the ocean for a person

“The eye, bhikkhus, is the ocean for a person; its tide consists of forms. One who endures that tide consisting of forms is said to have crossed the ocean of the eye with its waves, whirlpools, sharks, and demons. Crossed over, gone beyond, the brahmin stands on high ground. The ear, bhikkhus, is the ocean for a person…. The mind is the ocean for a person; its tide consists of mental phenomena. One who endures that tide consisting of mental phenomena is said to have crossed the ocean of the mind with its waves, whirlpools, sharks, and demons. Crossed over, gone beyond, the brahmin stands on high ground.” - SN 35.228