There's ten left.

However, if the question is how many are left alive, it's seven.

Someone's telling porkies!

If the fish are in a tank then how did 4 swim away.

As for drowning it's unlikely just 2 would drown for lack of oxygen and if they did are they included in the three fish you say died.

Personally I think the answer to your question is there are 12 fish in the tank because you fibbed about how many were in there in the first place