Exploring the Cerulean Coast in "Elden Ring: Shadow of the Erdtree" DLC seems to be an experience filled with both beauty and mystery, according to players and descriptions available. Here's what you might expect or want to look out for based on general insights from the community and available information:
Accessing the Cerulean Coast
•Via Ellac River: Start from the Castle Front Site of Grace, located just past the bridge after initially meeting NPCs at the crossroads in Gravesite Plain. Head east towards the deep valley, descending through waterfalls by jumping across rock pillars, and continue south to find the Ellac River Downstream Site of Grace.
•From Charo's Hidden Grave: This is an alternative path where players can use tombstones as ledges to descend from a high plateau directly into the Cerulean Coast, leading to the Cerulean Coast West Site of Grace.
Key Features and Points of Interest
•Exploration: The Cerulean Coast is known for its breathtaking landscapes, featuring blue waters, serene beaches, and hidden nooks. The area encourages free exploration, with numerous secrets tucked away in its corners.
Bosses and Enemies:
•Demihuman Queen Marigga: Located northeast from the Cerulean Coast West Site of Grace, she drops the Star-Lined Sword upon defeat.
•Dancer of Ranah: Found in the Southern Mausoleum after navigating an underwater tunnel west of the Cerulean Coast West Site of Grace, offers the Dancer's Set and the Dancing Blade of Ranah.
•Putrescent Knight: A remembrance boss in the Stone Coffin Fissure, accessible by heading south from the Cerulean Coast Site of Grace.
•Items and Collectibles: The region is rich with items, including crafting materials, weapons, and armor sets. Exploring thoroughly can lead to discovering unique items like Tibia's Cookbook.
Community Sentiment
•Posts on X and general feedback highlight the Cerulean Coast for its beauty, making it a memorable part of the DLC for many players. The sense of discovery and the visual aesthetics of the area have been particularly praised.
•Some players noted the challenge of navigation due to its less guided exploration style, which aligns with FromSoftware's design philosophy of rewarding thorough exploration.
Gameplay Tips 
•Be Prepared: Stock up on healing items and make sure your weapons are upgraded. The bosses here, while optional, can be tough.
•Explore Thoroughly: Many secrets, like hidden caves or underwater paths, lead to valuable items or shortcuts back to previously explored areas.
•Use the Map: Although the map might not provide explicit markers, paying attention to geographical landmarks can help in navigating through this expansive region.
Conclusion
Remember, while exploring, the game's design encourages curiosity but also caution due to the potential for hidden enemies or complex navigation puzzles. Enjoy the journey through this beautifully crafted region, where every discovery feels rewarding, and the atmosphere alone might make you pause and appreciate the world FromSoftware has created.