In Subnautica 2, there are several Biobeds with Endurance and Dexterity Adaptations to be found, which expand upon the number of inventory slots and tool slots respectively. The bunker locations of these upgrades are scattered around the Lifepod at different depths under the water.
Biobed #1
Head south-west from the Lifepod until you come across the wreckage of what looks like a wing about 20m down. Turn around until it’s to your north and look down for the entrance to a bunker. Use the Biobed, rather than just Scan it, in order to receive the ‘Endurance Adapted, Inventory Expanded’ benefit.
Biobed #2
Dive south-east of the Lifepod, going past the Welcome Center to your right. You will pass a pair of small pillars on your left with another one looming large further ahead on the right. Keep your distance as you face the large pillar so that it is to the south-west, and then look for a cave entrance about 40m down. You can also access this cave from the base of the pillar itself. Through the cave and to the right is another bunker with a Biobed and Endurance Adaptation.
Biobed #3
Journey about 200m to the north-east of the Lifepod until you come to a large chasm, then about-face to the south-west. You should be able to see the entrance to a cave clearly lit by a beacon around 30m under the surface. Head inside and to the left to find a third bunker with a Biobed and Endurance Adaptation.
Biobed #4
Note that this upgrade will require the Heat Tolerance Adaptation in order to access the general location.
Proceed due east of the Lifepod for just over 450m, going right past the glowing red pillars on your right until you encounter the wreckage of a gigantic chassis. Facing the wreck so that it is at 150 degrees, submerge to about 80 odd meters to find the entry point inside. Make a left into the first hallway, and left again into the first side room to find the fourth and final Biobed with an Endurance Adaptation.
By this point you ought to have 32 inventory slots in all.
Biobed #5
Head in the direction of 15 degrees from the Lifepod, going just past the weird four armed sculpture/organism to your left. Abruptly turn to the north-west and notice the platform about 35m down. Further to its left is a cave opening that goes straight down. At the bottom it will be difficult to orient yourself in this labyrinth, but try to proceed into an opening going north-west at 70m down. Once through, turn to the south-west to see the familiar glow of a bunker opening at about 85m down, with a Biobed and your first Dexterity Adaptation which improves Tool Quick-Access.
Biobed #6
The second and only remaining Dexterity Adaptation also requires the Heat Tolerance Adaptation in order to reach its general location.
Dive south-east of the Lifepod, continuing right past the familiar location of the bunker housing Biobed #1 beneath the large pillar. Keep going until you can submerge further below 50m into the fiery orange depths. Turn to the north-east and look for an underwater crevasse about 85m down. Once inside, make a quick left to find the bunker entrance at 90m underwater, with the last Biobed and its Dexterity Adaptation.
Those are the locations of all 4 Endurance Adaptations and 2 Dexterity Adaptations for maximizing the number of both inventory slots and tool quick-access slots in Subnautica 2.