Poseidon’s Trident Location (Breathe Underwater Perk)
Poseidon’s Trident is a legendary spear found in AC Odyssey. It can be found at the Temple of Poseidon, a very small island on the right hand side of the map. The legendary chest here contains Poseidon’s Trident.
It has a unique perk which allows you to breathe underwater forever. This is particularly helpful for the underwater locations required for the Child of Poseidon Achievement.