In hydrophilous pollination, pollen is primarily transferred by:
Hydrophilous pollination occurs when water currents carry pollen, a mechanism seen in some aquatic plants. This follows from NCERT principle where relation explains outcome clearly for students.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Biology - Botany portion covering relevant concept, Topic: Plant structure, physiology and applications.