Fish out of the water

When he was hunting, most of the creatures were not fast, agile or smart to escape if he set on getting them. Younger krakens of his school worshipped him, calling him immortal.
He decided to do what no kraken has ever done - hunt a sea wywern. He waited until one came close to the surface and attacked.
It escaped, but parked itself short distance away. He jumped and missed again.
Provoked, he tried once more.
His fourth jump ended on a quay - out of the water.
The wywern flew away cackling.
Desperately gulping for breath, he learned he is mortal...