Question

Okay water has a buoyancy force that lifts us and the gravitational force is less there but wasn't it explained that gravitational force is not affected by the medium surrounded

Answer 1

The answer is no.
I think the reason is that other forces are transmitte by particles that interact with the medium.
Gravitation is caused by the distortion of space and the medium has no influence, except to add mass and so cause its own effect on gravity.
But there is nothing that impdes gravitational attraction