Because the water cover the 外耳.(no dangerou)
You can jump 5-10 seconds. (head must 向下)
Or 跳水多一次.
Or use you hand輕力拍打ear (but 輕力) (not 插)
When you jump 5-10 seconds,
head must 向下 and head must 打側.
搭飛機,上高山,搭高 lift,
because you have 高山症.
find a doctor.
傷風鼻塞 can't be a answer.Because 傷風鼻塞 will have nose water and feel tired.
Or you do too long sport or too 劇烈sport.Then you feel not good.