There are two ways to get there. Walking (Overworld or not), or through the hidden underground passage in the northwest of Joppa.
Depth and ConnectionsEdit
Red Rock is 4 levels deep.
A river always spawns on level 4, running south. Follow it to access the Waterlogged Tunnel, from which you can enter the expansive Underground biome or reach Joppa by following the river south for ~6 screens.
The Girshlings on the bottom floor can be dangerous at lower levels. Level 4+ is suggested, and still be careful of drawing more than one at a time.
You can find a hidden passage to the Waterlogged Tunnel, which connects directly to Red Rock, by using the search command (S key) near the 2x2 square of water in the northwest corner in Joppa. This route is about as dangerous as traveling above ground. I find the underground route a little safer, since there isn't a chance of getting attacked by a Salthopper.
Flora and FaunaEdit
Red Rock seems to have the same spawning rules as the Underground biome.
Plus a small number of:
|Locations in Qud *|
|Salt Marsh >||Joppa - Red Rock - Waterlogged Tunnel|
|Great Salt Desert >||The Six Day Stilt ( The Stiltgrounds - Cathedral of Shekhinah ) - Trembling Dunes|
|Desert Canyons >||Rust Wells - Rusted Archway - Aspalt Mines|
|Flower Fields >||Bey Lah - Hollow Tree|
|North-Western Jungle >||Grit Gate - Golgotha ( Fetid Pools ) - Bethesda Susa - Garden of Geth|
|South-Eastern Jungle >||Kyakukya - Rainbow Wood - Tomb of the Eaters - Lair of Oboroqoru|
|The Spindle >||Banana Grove - Omonporch - Shadow of the Spindle|
|Chrome Ruins >||Deathlands|
|Rivers >||River Svy - River Yonth - River Opal - Opal's Duskwater|
|Others||Underground - Fungal Jungle - Slime Biome - Rust Bog - Snapjaw Fortress - Goatfolk Village|
|Mentioned Locations outside of Qud||Ekuemekiyye - Ibul - Yawningmoon|