In-ground swimming pools can have a lot of different finishes; they can be plain concrete, finished in vinyl, or with more expensive options these pools can be finished with tile. Over time, however, the tile in your swimming pool may lose its shine and develop mineral deposits, get coated in grime, and just become generally less appealing. That isn't a permanent state, however, and you can do lots of things to make your tile shine again.
First and foremost, the tile must be cleaned. This should be done once the pool is drained for the season and the tiles are open to the air. Heavy brushes and tile cleaning chemicals should be used and drained away. For some particularly stubborn tiles you can also use power tools that buff and scrub the tiles. Once the pool's tiles are cleaned and scrubbed, their initial shine should be restored. To keep that shine, though, you'll have to do a little bit more work.
To protect the shine on your pool tiles once they've been cleaned, you should apply a clear coating to them. There are specially formulated waxes that can be purchased as pool care stores, and there are also chemical coatings that can be put on over your pool tiles. These coatings will prevent grime from settling back on the tiles once the pool is filled up again. Monitor your pool's chlorine level, killing bacteria that cause grime and keeping the water safe for your family's use.