It would be cool to be able to see visibly discernable seagulls on beaches, particularly considering they are such a feature on many habitable ones in real life. They can be surprisingly bold when it comes to trying to steal food.
They could nick items that pirates leave on the shore to harpoon and move them around to be a hassle. To counter that, they could be chased off or something.
...Speaking of, dolphins would be also be cool to see. They could pop up alongside the ship when it is sailing at maximum speed, or when it initially entering a shallow area.
