Run by Misty, a Gym Leader who specializes in Water Pokémon. Misty is an attractive young women who also takes part in regional swimming races. However, she is very loyal to her gym and can often be found here if a trainer does wish to challenge her. The Gym itself has been transformed into a giant salt water swimming pool for the Gym Trainer's Pokémon to swim in, as well as for the Gym Leader and trainers themselves to keep up with their swimming practise.
Although it may not seem like much, the Bike Shop in Cerulean is the main distributors of bikes in the Region - for those who can afford them of course. They occasionally will offer promotional give-aways if you're lucky enough to be passing at the time.