How would a ship defend against a sea creature, and possibly win?

So this is a viking inspired race living in a harsh ocean based planet with very rough and cold seas. In these seas there are giant creatures, not unlike krakens or sea serpents, who frequently attack ships. I was thinking long and hard without and answer on how a ship ( eg viking longship ) could possible defend against one of these creatures, and win or at least drive it away.

Guidelines I guess:

  • the ship can’t end up like a floating pile of spikes and blades.
  • not pure strategies, I’m looking for realistic weapons, tools or design features that could possibly explain it.

Thanks in advance

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