Answer

You may be referring to Atimuktak (Aimatta), the child monk in Jain stories. He attained kevalgyan and then moksha after deeply repenting for a water-related act. ( jainqq.org)

Explanation

According to the story, Atimuktak once played with his patra like a boat in rainwater. Later, seeing children playing in water reminded him of that fault. He sincerely repented, recited the Iriyavahiya Sutra, and attained kevalgyan and moksha at the age of 9. ( jainqq.org)

Spiritual Understanding

This story teaches that in Jain Dharma, true repentance and inner purity are very powerful. Even a small mistake, when remembered with sincere remorse and purified through right awareness, can become a turning point on the path to liberation. ( jainqq.org)

Takeaway

So, the name commonly linked with this kind of water-related moksha story is Atimuktak. ( jainqq.org)