For the similarly named zone in Diablo III, see Tidal Cave.
"Good. To the north, that's near the Planks. There's a cave not far off that should get us closer to the keep."
Tidal Cavern is a quest-specific zone of Stormpoint seen in Diablo Immortal. It is available only in the storyline quest "the Planks".
Lore
The Tidal Cavern is an underground sea cave located in the Planks. The Cult of Terror used it as an extension of their lair; which was located directly above the cave.[1] It has another exit at the Ship Graveyard.[2]