Drop into my clinic. Before you entered the water you had wax partially occluding the ear, so it did not affect your hearing. However when you entered the water, the water went beyond the wax and got trapped between the wax and your eardrum causing the "Occlusal Effect" or blocked ears!
Next Steps
Use this app to fix up an instant appointment with me at my clinic Healthcare@Basaveshwaranagar and let me clean your ears gently with my microsuctioning tools.
Health Tips
Use silicone earplugs in future to waterproof ears while swimming(available at my pharmacy for Rs75).