First, you need to find the Old Complex with the Biolab.
It's not far from your spawn point, being southeast.

Once you have found the structure, you will need a Basic Battery to power it.
After restoring power, the lights will turn on, allowing you to interact with the Biolab inside.

You can choose 2 different upgrades:
- Active Biomods
- Passive Biomods
Eventually, you can have multiple passives but only 1 active.
The first active is the Dash ability. It has a 5-second cooldown and can be used to increase mobility or get out of danger.

There are also 2 passives to choose from; the one we want is the Sea Skimmer.
This increases your movement speed when you are close to the seafloor.