Al-Husayn ibn Said, from Muhammad ibn Abi Umayr, from Hammad, from al-Halabi, from Abu Abdillah عليه السلام, peace be upon him, who said:
Imam عليه السلام said: “The fasting person may immerse himself in water, but he must not submerge his head.”
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 4, p. 268