Could aliens be living in our oceans?

There is no scientific evidence that extraterrestrial aliens are living in Earth’s oceans.

It’s true that the deep ocean is still not fully explored, and scientists continue to find new species and unusual ecosystems there. Deep-sea environments also host extremophiles that can live without sunlight, often relying on chemosynthesis instead of photosynthesis. Astrobiologists study these ecosystems to help understand how life might exist on other worlds, including ocean-bearing moons such as Europa and Enceladus.

So, could it be possible in a purely speculative sense? Maybe — but there is currently no evidence that aliens are living in our oceans, and the extraterrestrial-alien explanation remains unsupported by science.