In a game I'm in we have ventured underwater into the ocean. I play a summoner, my eidolon has gills, a swim speed, a Bite, 2 claws, and a tentacle attack. How would being underwater effect his damage output?
I've read through all the rules on underwater combat I could find however it didn't fully answer my question regarding natural attacks.
Land-based creatures can have considerable difficulty when fighting in water. Water affects a creature's attack rolls, damage, and movement. In some cases a creature's opponents might get a bonus on attacks. The effects are summarized on Table: Combat Adjustments Underwater. They apply whenever a character is swimming, walking in chest-deep water, or walking along the bottom of a body of water.
The chart after lists the effect of freedom of movement spell, swim speed and piercing vs. non piercing weapons, but I don't see anything explaining how does natural attacks are affected by being underwater.