Oceanside Dungeons

This new variant of the dungeon would only generate in the new Oceanside Cliffs biome.  They would be made out of Brownstone Bricks.  The entrance to the dungeon would look like the mouth of any ordinary cave in the side of the cliff.  The dungeons would only generate when the cliffs are at least 15 blocks high.  The dungeons would always spawn cave spiders, so that they can pour out of the dungeon and climb up and down the cliff, trying to kill the player.  For this extra trouble, the player would be rewarded - instead of getting just 1-2 chests, the dungeon would always contain 3 chests.