They are easier to find while riding a raft, having a monkey on your shoulder, and having a beard. It is recommended to have a big raft that looks like a pirate ship. The ship must have cannons.

When the tusoteuthis grabs you you can avoid its attacks by firing an arrow at its beak during the attack

Easy to find when on a submerged tame. Must have 3 compliant captives on board and you will be attacked on a semi regular basis

When you see one of these, be ready to die.

Be extra careful around them, when exploring the sea caves, as they can grapple your dino (even your mosasaurus).