As soon as you start playing Dave The Diver, you'll embark on a journey to find out more information about the Sea People. Eventually, you'll enter their village and their ruler will ask you to find a special key from the Abandoned Cave. You'll use the key to go down to the control room and find the reason for the temperature increase.
Once you reach the control room, Dr. Bacon will ask for a couple of days to tear through the tree branches so you can enter. During these days, you won't have any main quests and the control room entrance will have a special animation with the laser device.
How To Remove The Tree Sap
As you enter the room after the branches are cleared, you'll see that the passage on the left is blocked by tree sap. You'll also see a snail moving on the floor in this room. Pick the snail up and place it on the platform with chains on the top right side. This will open the way to the right and you can go through.
Snails will start moving a few seconds after you place them somewhere, so you have to be quick.
In the next room, you'll see a bunch of scorpions and some Divine Fruits on the tree branches. Make sure you get rid of all the scorpions first as they can be quite a nuisance. After defeating the scorpions, pluck out one of the Divine Fruits and throw it on the sap below. You have to be quick with this because the fruit explodes soon after you pick it up.
Head down and simply throw the snail on top of the hydrothermal vent. This will stop the pressure coming out of it and you can head further to the left. The next section is the hardest because you have to time the position of the three snails quite well. Start by placing one snail on a distinct platform just above the vent to the right.
This snail will slowly start walking and automatically fall on this vent. While it does that, throw the other two snails on the other vents as fast as possible. After trying it a couple of times, you'll succeed and the passage above will open. Use the Divine Fruit to get rid of the sap on the left and head further in.
How To Reach The Final Boss
In the next part, you'll have to maneuver through some toxic vents. If you hit any of these vents while they're erupting, you'll take around 50 to 60 damage to the oxygen. For the first set, you can simply wait just before each vent until it calms down and then cross it. In the next set, you'll have to go down while the vents will be slanted.
Simply wait near the vent's base until it stops erupting and then get past it. In the final few vents below, you can use the two snails on the floor to block the first two and then cross when the third one calms down. You'll start seeing a lot of white goo and eggs in the next room.
Some hatchlings will appear from the eggs as soon as you enter. Use your Harpoon to defeat these enemies since they have very low health. Don't try to use your weapon since their sheer number will easily get rid of all your bullets. After defeating the hatchlings, you have to use the snail on the floor to open the next door again.
In the next room, place the Divine Fruit inside the device and use its lasers to defeat all the enemies. Make sure you defeat the enemies from top to bottom since this makes it much harder for them to get to you. If an enemy crosses the laser's range, leave the device and defeat it with your harpoon.
You'll have to defeat three waves of these hatchlings, and each time their number will increase.
After defeating them all, you can use the laser to melt the white goo on the door to the right and enter the core room. In this room head to the top and hit all the hatchlings stuck to the core. This will lead to the introduction of the final boss called Yawie. You'll also get a brand-new weapon just for this boss fight.
Use the weapon to hit the boss on the head or the body as much as you can while dodging its attacks. If the boss does an attack where it spawns a bunch of red bullets that circle the area, focus on dodging this attack first. Every few seconds, a few of these red bullets will come directly at you.
The new device in your hands also helps you slow down time. Do it as soon as you see the red bullets coming to you.
This will let you easily dodge them all.
The rest of the boss fight is quite intuitive, but dodging its attacks will be the hardest part. You'll also get an upgrade to this weapon that lets you charge a lethal laser. This laser will also remove all the projectiles spawned by the boss.