There's never a shortage of unique visitors to the Blue Hole in Dave the Diver and Ichiban is the latest to stumble across Bancho Sushi in the Ichiban's Holiday DLC update. A special quest sees Ichiban and Dave team up to take on Sea Blue and stop their latest antics, and here's a guide for how to unlock and complete it.
The Operation Sea Blue Eradication quest is the focal point of the Ichiban's Holiday DLC update, but it does have some requirements to unlock it in-game.
First, you need to have the Ichiban's Holiday DLC purchased and downloaded for the base game. Patch notes for the update indicate that this DLC will only be available to purchase and download until October 9, 2025, so make sure to grab it before then.
Once done, you then need to progress the main story of Dave the Diver up through the end of Chapter 5: Melting Glacier. After starting Chapter 6, during night hours at Bancho Sushi, you'll be introduced to Ichiban himself (also known as Kasuga) and the Bartender, who are visiting the area. After a brief conversation, they leave the restaurant, and this kicks off the DLC's storyline.
The following day, Kasuga will greet Dave and Cobra on the water. Soon after, a dolphin suddenly appears near Kasuga, seemingly crying for help. A boat full of pirates then pulls up, who have the creature in their sights. Kasuga climbs onto the boat and makes short work of the pirates.
Afterward, he returns to talk to Dave and Cobra, who mention that said pirates work for Sea Blue, a nefarious group disguised as an environmental protection agency that's been harassing Dave for some time now.
Kasuga offers to help take the fight to them, and Cobra obliges by offering up a timed explosive to help break into their nearby base. However, they insist on waiting until the Evening to infiltrate. From there, the quest officially begins.
Either time skip to Evening, or take care of any other fishing tasks you need to before then. Either way, once the sun sets, Kasuga will return to the boat, ready to start the operation. Cobra puts Dave in charge of ferrying the bomb while Kasuga escorts and protects him from any threats.
At this point, you'll assume control of Kasuga while escorting Dave underwater.
After they're dealt with, approach the entrance to Sea Blue's base, and Dave will go plant the bomb to blast it open.
Once Dave and Kasuga are inside the base, Cobra will soon join up to help. You're put in charge of both Kasuga and Cobra for the fights ahead. The game will display a classic fight menu, prompting you to choose which character you want to fight with first, along with your basic fight controls.
From this point, you'll have to take on waves of different enemies using both Kasuga ("Ichiban") and Cobra. You can use the appropriate button to switch between them during fights, to better control damage and defense. Each character gets a total of four lives during each stage, and there is a time limit to keep an eye on.
Punch your way through each wave, which consists of:
Eventually, you'll reach the lab where an evil scientist named Torben is revealed to be experimenting on captured sea life. He threatens to not let you leave alive, and a boss fight against him ensues that consists of multiple stages.
During the first stage, he'll brandish a shotgun, and you need to be careful to avoid it while taking down his health bar. In the second stage, he'll break out his experimental weaponry that gives him a shield and fires a deadly laser beam. Be careful when he blocks your attacks, and knock him out to finish the stage.
During the final stage, he'll amplify his experimental weapon and boast three bars of health and shields. Follow the same formula and finally defeat him. Dave arrives soon after as the base self-destructs and all three escape. The quest will end back on the surface soon after.
Be sure to check out all of the latest gaming guides and news at Pro Game Guides, such as our Ultimate Half Sword Weapons guide and tier list.
