Since Walking Wake has Water as its Tera Type, that means your best bets are all the types that are super effective against Water: Grass and Electric.
Related: Pokemon Scarlet & Violet: Best Steel-Type Pokémon, Ranked If it doesn't, you can just repeat the process. This resets all the dens (as well as the outbreaks if you'd like to hunt for shinies) on the map into new ones, which could potentially make the Event Den spawn. If you don't see any Walking Wake Tera Raid Dens, you can change your clock's time in the System Settings to one minute before a new day begins (11:59 PM) then go back into the game to wait for the day to change. It will also sparkle noticeably in the overworld. Additionally, Walking Wake will only have Water as its Tera Type, so that narrows it down even more. You'll be able to tell the den from the rest of the normal ones by the way it sparkles on the map. If you have Pokémon Scarlet, you can just look on your map for an Event Tera Raid Den. If you have Pokémon Violet, you will have to either join the Tera Raid of a friend that has Pokémon Scarlet through a Link Code or look to the Tera Raid Board for anyone hosting a raid of Walking Wake online. Walking Wake is also only found in Tera Raid Dens in Pokémon Scarlet. If you haven't completed the game yet, you have plenty of time to do so before the event ends. After that, Professor Jacq will call you and notify you that the harder Raid Dens are popping up. In order to unlock the dens of that difficulty, you'll have to complete the game and view the end credits. Walking Wake resides in 5-Star Tera Raid Dens.