1a. We were sinking in the sea.
1b. We were sunk in the sea.
1c. We were drowned in the sea.
2a. The ship is sinking in the sea.
2b. The ship was sunk in the sea.
2c. The ship was drowned in the sea.
Please comment on my above sentences.

I am also enthusiastic about these question.

They are all possible.

I interpret “sunk” in 1b and 2b as a passive verb form, rather than an adjective. I’m not sure what your intention was.

If “drowned” is meant literally then 1c could only be said from beyond the grave.

It is not very common to say that ships “drown”.

I can’t work out your sentence. Could you please explain it to me?

It means the people who say this sentence are already dead when they say it!