Aquaria

Aquaria is a 2D sidescrolling action-adventure game, heavily focused on exploration and puzzle-solving, with non-linear gameplay. The player controls Naija, a lone underwater dweller; although similar to a human woman, Naija also has several fish-like qualities, such as the ability to breathe underwater and propel herself quickly with webbed feet.

In general, Naija cannot interact directly with objects in the world. Instead, the majority of actions are accomplished through singing short tunes. Singing notes affects plants and objects of the same color as the note, while singing the tunes, once learned through the plot, can lift objects, create a shield around Naija, or change Naija into different "forms" which have different appearances and unique abilities critical to overcoming the various challenges and obstacles found in the game.

From the official website: A massive ocean world, teeming with life and filled with ancient secrets. Join Naija, a lone underwater dweller in search of her family, as she explores the depths of Aquaria. She'll travel from hidden caves, shrouded in darkness, to beautiful, sunlit oases, all lovingly handcrafted by its two creators.

Naija's story, narrated fully with voice overs, will become yours, as you join her on this magnificent adventure.