Which animal survived outside the teiva? I know og melech havashan survives but which animal?
Welcome to Mi Yodeya.
No animals survived as it says 7 (21):
And all flesh perished that moved upon the earth, among the fowl, and among the cattle, and among the beasts, and among all creeping creatures that creep upon the earth and all mankind.
But the fish survived as can be seen in Zevachim 113b
דאמר רב חסדא בדור המבול לא נגזרה גזרה על דגים שבים, שנאמר מכל אשר בחרבה מתו, ולא דגים שבים.
Rav Chisda said “in the generation of the flood, there was no decreee against the fish in the sea as it says, “all that was on the dry land died” Braishis 7 (22) and not the fish in the sea.
@chacham Nisan rightly corrects my answer to say that the re'em was too big to enter the teiva so it survived by putting its nostrils in the teiva. The following are sources
Zevachim 113b where the animal is called the “reima” “רימא" and
They also say the Leviathan survived as it is a sea creature.