I believe it would be less impactful than many power plants that vent their heat into the ocean. There are many studies, mainly around marine life (phytoplankton, manatees, other endangered species). These systems probably produce similar heat output into the water.

https://assets.nrdc.org/sites/default/files/power-plant-cool...

https://www.sciencedirect.com/science/article/abs/pii/S00253...

https://res.mdpi.com/d_attachment/water/water-11-02577/artic...