you will probably have noticed that your ears do funny things in an aeroplane, or on a train when it drives into a tunnel, in a car when you drive up (or down) a mountain, when you go diving, or when you have a bad cold.
Most people describe the sensation as a 'pop' and can 'equalise' (restore their ears to normal) by holding the nose closed whilst attempting to blow down it.
This works because the ear consists of an outer ear canal (the bit you can put your finger into) which ends in a thin membrane called the eardrum. The eardrum seals off the ear canal and prevents things, including fluids, from moving any further into the ear. Behind he ear drum are your body's three smallest bones, known as the ossicles, the malleus, incus and stapes (hammer, anvil and stirrup) which convey vibrations from the eardrum to the cochlea, the ear's nerve centre where sound is converted into electrical nerve energy. The space that the ossicles (ear bones) sit in is called the middle ear cavity, and it is connected to the back of your nose via a thin passageway called the eustacian tube. There are two, one for each ear. You need these tubes so that sound waves can compress the eardrum, otherwise whenever a sound wave tried to make the eardrum vibrate it would have to compress the gas in the middle ear, making it difficult to hear any quiet sounds.
As your nose is connected to your ears, if water flies up your nose sufficiently quickly it can be forced along the eustacian tube and into the middle ear cavity where it produced unpleasant squelching sensations ! It is slowly absorbed by the cells lining the cavity, and also disappears by evaporation, but it can take a few hours.
This is why people abandonning a ship, or jumping feet-first into water from a reasonable height, are advised to hold their noses. Otherwise the nose acts like a great funnel and collects water to ram into itself...with very unpleasant effects !
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx