Answer:

THERE ARE 10 FISHES LEFT IN THE TANK.

Explanation:

CONSIDER:

10 fish are in a tank.

-Two Drowned

-Four Swam Away

-Three Died

Answer:

-Fish do not drown

-They can't swim away

-3 are floating inside the tank

So in conclusion, ALL TEN FISHES ARE STILL LEFT IN THE TANK.

(By the way, this is called the "10 Fish In A Tank Riddle". :>)