Katherine Sunday (also spelled Catherine Sunday) is the main assistant and only other main character in Endless Ocean, residing on the Gabbiano, the player's trusty boat.

Behavior and Personality

Katherine is friendly and amiable, warming up to the player right away. She frequently offers advice and directions, either through talking conversation on the boat, notes on her notice board on the cabin window, or communication via a radio somewhere on the player character's suit.

Though she cannot swim and fears swimming (hence why she wears a life vest all the time), there is a camera on the player's diving suit somewhere that she receives video feed from, which allows her to see all that they see. As such, she can provide them with directions, instructions, advice, knowledge, and other comments.

Katherine is very intelligent and intuitive, and appears to have the ability to understand animals on a basic level; she can read their body language and vocal signals to translate what she believes they are saying, as was first displayed in the presence of an African Penguin that climbed up onto the player's boat. She also has extensive knowledge about artifacts and oceanic archaeology, as can be surmised from the surprisingly extensive information she provides the player with whenever they recover a salvage item of importance or discover a unique area. Nonetheless, she frequently contacts people who know more than she does in order to give the player more information.

She seems particularly uneasy about the Deity Idol, a small figurine described as "ominous" in the player's footlocker.

Her most common nickname is "Kat" - a coworker and friend of hers, Douglas Banner, refers to her by it whenever he talks about her over email.

Some of Katherine's dialogue, namely her usage of the word "mate" as a way to refer to the player, might hint that she is from Australia or the UK.


Warning Spoilers for Endless Ocean ahead!
Katherine was fascinated by ocean life from a young age. Her father, Patrick Sunday, was a scientist and sailor who died whilst searching for the Ancient Mother (presumably by drowning). Katherine's goal is to find the White Mother and finish her father's quest, but her inability to swim held her back until the player character came along. It is unknown where her fear of swimming came from, although it can be assumed that it might have had something to do with her father's death.


  • Katherine has a fairly large fan base. Her kind and friendly personality was often seen as a very welcoming factor to the game. When Endless Ocean: Blue World was announced, many people were eagerly anticipating her return however she was replaced with a similar looking shorter girl named Oceana. In early screenshots Oceana was mistaken for Katherine without her glasses, some people even thought it was Katherine's cousin. Her removal from the sequel angered many fans and Oceana does not appear to have received the same amount of popularity.
  • Katherine is often criticized for the uselessness of her comments. Normally when talking to her, she comments upon the current mission the player should focus on, or she makes a randomized comment or states a random fact. Game reviewers stated that Katherine looked too robotic and took away from the game's atmosphere. The critics also complained about her pointless dialogue. For example, when the Idol treasure is reconstructed she says something along the lines of "I have a feeling something bad will happen if I reconnect these pieces... Oh well, let's do it anyway".
  • Some speculation has arisen as to why she was not featured in Endless Ocean: Blue World. One rumor is that she was fired for being unable to swim and be of more use, whereas another rumor suggests that her findings concerning White Mother have led her to fame and fortune, meaning she no longer needs her job as a secretary.
Warning Spoilers for Endless Ocean end here.


  • Catherine's idle pose that she takes while looking at the sea off of the stern of the boat.
  • Catherine with the African Penguin that introduces players to the mechanic of interacting with wildlife on the boat.
  • An idle pose that Catherine takes up prior to speaking to the player during one cutscene.
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