All Boss Cards and Where to Find Them

This guide will show how to get all the boss cards and how to access them, it will alsp provide some sort of tips to be able to defeat the bosses.

All Boss Cards:

Clione Queen
This one can be found by completing the tasks of collecting 5 cliones by catching them through the net, once collected the boss will appear and swallow Dave bringing it to it's nest, upon being able to defeat the boss, it will drop meats as usual. In order to access the area, Dave must be equipped with enough suit to go into the deep because that's where the boss will appear.
Kronosaurus
Kronosaurus is the boss from the Hydrothermal Vents, it will only appear once Dave got the chance to go though the Hydrothermal Vents, it will not be accessible unless Dave gets his hands on a solution to counter the heat coming up from the Hydrothermal Vents which requires finishing the two available caves from Glacial Area to reduce the heat coming up from below. Once completed, going through the Gate from where Dave can access the Control Room, the Kronosaurus will appear by the right side where there will be moving debris.
Mantis Shrimp
Mantis Shrimp is coming from a vortex from Stormy Night 2, it will only appear when Dave has completed Stormy Night 1, if by any chances, Stormy Night 1 came and Dave missed it, it will re-appear again in a few nights or so. Once the card collector NPC comes, Dave must dive at the same night since missing it will cause the event to re-appear. The vortex can be found near the shallows.
Giant Squid
When retrieving box from the sunken yellow ship, the giant squid will appear and can be hinted multiple times, just follow through the missions wherein Dave has to retrieve a delivery box from the sunken yellow ship. This is the first boss card so it may be hard to miss.
Giant Wolf Eel
After getting a sea people translator and making a soup to heal Ramo in the blue hole depths, Dave will be tasked to carry Ramo back to the Sea People Village, later on it will require Dave to get diving gloves to pull debris off and break the path connecting to the Sea People Village, before being able to enter the Sea People Village, there will be an area that Dave has to pass through which he would be able to fight with the Wolf Eel.
Phantom Jellyfish
Once Glacial Area is unlocked, all you have to do is finish the first Glacial Cave and then a prompt wherein Dave would want to check the second Glacial Cave, before doing this I suggest going back to the Sea People Village and helping Ramo locate the Beluga Whale which later on may be used to pass through the second Glacial Cave. The Beluga Whale can be found somewhere on the left area of the Glacial Area, near the entrance for the Glacial Cave. Dave will be riding the Beluga Whale and avoid the obstacles on the way to the Phantom Jellyfish, in order to defeat the Phantom Jellyfish, Dave must use the Beluga Whale to dash through the eyes of the Phantom Jellyfish.
Goblin Shark
To access this, there will be a mission wherein Dave has to gain the trust of the People in the Sea People Village, I suggest taking the mission of the Children with missing ball first. The second time they come to you, they will say that one of their friend is missing and that Dave has to find the missing kid. You will have to follow the signs previously can be seen at the depths which leads to a new area wherein you'll encounter the Goblin Shark.
Great White Shark Klaus
One of the NPC's will come to Dave at night telling Dave that there is a vortex underwater that you may find a boss card, this mission is called Stormy Night 1, the vortex will just be in the right corner when you dive at night, I suggest getting a sniper rifle or equipping a much higher level of oxygen to be able to withstand the attacks of Klaus. The shark is very fast and takes about 50-60 damage when you get hit.
Truck Hermit Crab
This boss is also part of the Stormy Night sub-missions, in this boss you can easily dodge the attacks by trying to go behind it, it cannot rotate and only goes forward and backwards and give you a lot of time for aiming, to defeat the boss Dave would have to pick up an explosive barrel that will appear on the ground when the boss bangs the ground, Dave then will have to drop it by the shell, removing the wheels of the truck one by one.
Helicorpion
This boss can be found upon trying to complete the third Glacial Cave, easily you will get help from one of the sea people although not much, it's easy to avoid the attacks since it acts like a normal shark. To defeat it, Dave can use a combination of hitting the divine tree fruit to stun it and then shooting it with the Harpoon or a gun. After multiple times of doing this, it will try to escape meaning you're closing in to defeating the boss.
Yawie
To kill Yawie there will be series of levels to defeat it, to get to this point, Dave must be able to access the Control Room then follow the path through which Dave will encounter the eggs of Yawie, killing it, for me, is the easiest and most fun way of defeating a boss, there will be no such guns needed, you will just have to up your dodging game.