These two similes both use fish. The first compares a mind caught in Mara as a fish flopping about on dry land.

As an archer aims an arrow, the wise aim their restless thoughts, hard to aim, hard to restrain.

As a fish hooked and left on the sand thrashes about in agony, the mind being trained in meditation trembles all over, desperate to escape the hand of Mara.

Hard it is to train the mind, which goes where it likes and does what it wants. But a trained mind brings health and happiness. The wise can direct their thoughts, subtle and elusive, wherever they choose: a trained mind brings health and happiness.

The Dhammapada, Eknath Easwaran translation (Mind)

The second likens pure awareness (the Self) going between waking, dreaming, and non-dreaming states to a fish swimming between the banks of a river.

The Self, pure awareness, shines as the light within the heart, surrounded by the senses. Only seeming to think, seeming to move, the self neither sleeps nor wakes nor dreams… As a great fish swims between the banks of a river as it likes, so does the shining Self move between the states of dreaming and waking.

The Upanishads, Eknath Easwaran translation (Brihadaranyaka Upanishad)

I experienced life most often like the first fish. What little faith I have is as follows: if certain conditions are met by the way I live, through my practice of meditation, by loving, and by acting humbly, I can live life more often experienced as the second fish, in contact with the pure awareness that underlies experience.