In the Chinese Mahayana Practice, there is this ritual of invoking blessed water through recitation of the Great Compassion Mantra.
This mantra is closely related to the popular Bodhisattva of Compassion. Kuan Yin.
The blessed water is being drank by devotees to seek blessing or given to the sick .or anyone suffering from spiritual disturbance.
The person invoking and consuming the water must have faith. (The mind plays an important role)
The person invoking the blessed water should be someone with compassion.
That person should not have committed grave faults such as killings etc. Basically, someone who observe the Buddhist precepts.
How to invoke the blessed water.
Prepare a glass of clear water
Step 1 – Recite refuge prayer
Step 2 – Invoke the blessing of Bodhisattva of compassion, Guanyin by thinking about this Bodhisattva and praying for blessing
Step 3 – recite the great compassion mantra in front of the water
Step 4 – state the reason for invoking the blessed water
The water can be consumed.
The Great Compassion Mantra
Sarva sattva nama varga.
Kuru kuru karmam.
(Kuru) Kuru vijayati
Basa basam presaya.
Hulu hulu mala.
Hulu hulu hilo.
Namo aryavalokitesvaraya svaha.
There was study conducted by a Japanese researchers on the power of prayers on water. He tried to see if there’s any effect on the water by using modern technology.
Here’s a link.