In Endless Ocean, the player can choose only three out of eight available species (because the Narwhal, Spectacled Porpoise, and Amazon River Dolphin do not appear in the first game) to have as partners. The first partner the player can obtain is a bottlenose dolphin that had somehow become separated from its pod and became confused, because its echolocation was befuddled by the shallow waters of the Lagoon and Coral Forest. The player helps get it to deeper waters and thus gains its trust, meaning that the player will always have at least one dolphin partner all throughout the game.
To befriend a dolphin, the player must simply find the dolphin they want to befriend (any individual of the species, anyway), and learn as much about it as they can (unlocking each of the three information slots) and then continue to behave as if they are still learning about it; that is, continue to feed it, pet it, and use the sea whistle on it as much as possible. (There is no outward indication of when the player has interacted with the dolphin enough to befriend it, so lucky guesswork plays a minor role in this process.) Then, when they return to the boat, Catherine will note that a dolphin has come to the back deck of the boat to see the player, at which point the player can choose if they want to keep the dolphin, and, if they do indeed keep the dolphin as their partner, a name for their new friend.
The dolphins in the first game can also learn tricks, but not as specific or as easy to teach as they are in the second game. They player can train these tricks by using the Sea Whistle off of the back deck of the Gabbiano, which happens automatically when the player selects the stairs that lead to the gangplank.
Endless Ocean: Blue World
In Endless Ocean: Blue World, the player can befriend a total of eleven species. However, unlike in the first game, the player cannot befriend just any specimen, and instead must follow specific steps in order to befriend certain individuals from each species.
Some partners are gained simply through playing through the game, while others require the player to complete the Be the Best Trainer quest. The befriendable dolphins are unique amongst other members of their species through defining traits such as having strange markings, unusual coloration or differing size.
The first partner you can befriend is a short-beaked common dolphin with a golden tail. This dolphin is already an ally of L&L Diving Service by the time the player meets them, so befriending them is automatic.
The second partner you can befriend is a spectacled porpoise with white markings. Befriending them is part of the main story, as the porpoise helps guide the player out of the Weddell Sea during a severe blizzard.
The third partner you can befriend is a bottlenose dolphin with albinism. They can be found at Cross Rift in Ciceros Strait, being attacked by a tiger shark. After calming the shark, you gain the trust of the dolphin and they befriend you.
The eighth partner you can befriend is a white-finned pacific white-sided dolphin. They can be befriended during the Be the Best Trainer quest, by visiting them multiple times until they feel comfortable.
The tenth and penultimate partner you can befriend is a smaller-than-usual orca. They can be befriended near the end of the Be the Best Trainer quest, by letting it interact with Hayako and giving it a plastic toy.
The eleventh and final partner you can befriend is a white-marked Commerson's dolphin. They can be befriended at the end of the Be the Best Trainer quest, by offering gifts to the Queen of the Okeanos. After finishing this quest, Finley, the man behind the quest, will declare you his eternal rival.
All dolphin partners will learn six tricks, and some can be upgraded into better and more complex tricks after leveling up. To train these tricks, the player can call their dolphin partner to them using the Dolphin Bell on Nineball Island.
Level One Tricks
All dolphins learn the same tricks at level one:
- Jump/Flip - The dolphin jumps out of the water.
- Sing - The dolphin "sings" a song.
- Backflip - The dolphin does a small backflip out of the water.
- Wave - The dolphin positions itself horizontally in the water and waves its front fins in a similar manner to the human greeting.
- Spin Jump - The dolphin does a small vertical jump with a little bit of spin.
- Tail Walk - The dolphin propels itself across the surface of the water using its tail fin.
Level Two Tricks
All dolphins learn the same tricks at level two:
- Advanced Jump/Flip - The dolphin does a larger jump, while flipping faster.
- Sing - The dolphin sings a different song than the level one song, and longer.
- Advanced Backflip - The dolphin performs a bigger backflip, while flipping faster.
- Wave - Nothing changes with the wave trick, except a slight increase in duration.
- High Spin Jump - The dolphin does a higher spin jump, while spinning faster.
- Tail Walk - Nothing changes with the tail walk, except a slight increase in duration.
Level Three Tricks
Some tricks may be replaced by a special trick. These are the defaults:
- Super Jump/Flip - The dolphin does an even larger jump, while flipping even faster.
- Sing - The dolphin sings a different song.
- Super Backflip - The dolphin performs an even larger backflip, while flipping even faster.
- Wave - Nothing changes but for a slight duration increase.
- Corkscrew - Your dolphin performs an even higher spin jump, while spinning rapidly.
- Tail Walk - Nothing changes but for a slight duration increase.