A week ago I was swimming in the sea and abruptly I felt water flowing into my left ear. It caused pain that later increased. I tried to get the water come out of the ear (jumping on one foot etc), but nothing helped. Since then I keep feeling this water in my left ear.
Yesterday I went to an ear doctor (ENT) who just looked into my left ear and told me I had an inflammation there and prescribed antibitotic. I asked her whether there was still water in my ear. No water, she said.

But I still feel that something (water?) is behind my eardrum and I don't understand how the doctor could see what is behind the eardrum. I am afraid if there is water there, the inflammation can't be healed and it will only worsen.

My question is: Is it possible that water flows behind the eardrum into the middle ear and it stays there days long and do not come out (e.g. through the Eustachian-tube)?