Corrector Yui Book 3 — Kia Asamiya

Yui Kasuga was an ordinary girl at an ordinary school that is, until the day she was sucked into the Com-Net and asked to save cyberspace from the evil virus Grosser and his minions.
With the help of her friends, the Corrector Programs, Yui is sent to the Marine Adventures digital theme park to beta-test the program before the public is invited. Her trip to the beach is no picnic when Grosser himself turns up to contaminate the whole thing. It will take the song of a whale and the love of a girl to save this part of Com-Net.