Startide rising.

David Brin: “Startide Rising” (1983) This is a sci fi story about a Terran (Earth) crew of neo-dolphins and humans on the starship “The Streaker”.
Their mission is to find information about the first Galactic race, which existed billions of yeas ago. The neo-dolphins are dolphins which have gone through the "Uplift" process, which creates through genetic engineering more intelligent sentient beings. For the neo-dolphins, this is also a test of their ability to apply their intelligence, knowledge and skills to Galactic space travel and exploration. The Terrans find an ancient fleet of starships, and on a nearby planet, an ancient (human?) skeleton. There are other Galactic races, who are also keen to find information about the first Galactic civilization. Their hot pursuit of the Terrans forces “The Streaker” to land on the planet Kithrup, whose watery environment and atmosphere are similar to Earth. Above the planet, the starships of the other Galactic races fight each other.
On Kithrup, the dolphins and humans begin repairs to the Streaker, and to explore the ocean, and the inland area of their landing site. They discover an aboriginal species living amongst the trees and lakes inland. There is evidence that there has been another Galactic race on the planet in the very distant past.

Within the crew of the Streaker, tensions and conflicts develop on how to escape from Kithrup. The story centers on individual human and dolphin characters, and their struggle to survive and eventually to return to Earth with their very important findings. The story becomes one about courage, determination, friendship, love, and betrayal, both for the humans and the dolphins. Main human characters: Gillian Baskin, Tom Orley, Ignazio Metz. Main neo-dolphins: Captain Creideiki; Hikahi; Keepiru; Makanee; Takkata-Jim.