Subnautica Modded Survival Guide: Deep-Sea Base and Gear Tips

To survive high-pressure environments and steep resource demands in modded Subnautica, your immediate priority is establishing sustainable oxygen refills and reliable base power before diving past the 500-meter threshold. Standard oxygen supply and surface solar reliance fall short in deep biomes, making tactical gear upgrades and specialized outposts mandatory for progress.

How to Manage Oxygen on Deep Expeditions

Standard air tanks cannot sustain long dives in high-pressure sectors. To extend your underwater operational time, execute the following measures:

Equip High-Capacity Gear: Craft high-capacity oxygen tanks as early as possible. Keep a spare, fully charged oxygen tank in your inventory when storage space allows.
Build Oxygen Relays: Construct small, minimal outposts consisting of a single base corridor and a solar panel near deep biome entrances. These act as emergency breather stations, preventing long backtracks to the surface or your main vehicle.
Deploy Mobile Bases: Use oxygen-generating vehicles as mobile operating hubs so you never rely solely on internal suit air during long mining runs.

Powering Deep-Sea Bases with Thermal Energy

Solar panels become ineffective in dark, low-light depths. For deep bases—especially near volcanic vents—thermal power provides continuous electricity to support high-drain machinery like water filtration systems and battery chargers.

Scan for Thermal Vents: Locate heat sources on the seabed using your scanner.
Place Power Transmitters: Position transmitters directly adjacent to vents to achieve maximum voltage output.
Use Bioreactors as Stopgaps: If geothermal heat is not immediately available, build a bioreactor using local organic material. Treat this as a secondary power source, as organic fuel requires constant manual refueling.

Critical Upgrade Materials and Priority

Modded progression increases crafting costs for advanced depth modules and base structures. Prioritize collecting rare minerals early to avoid progression bottlenecks.

Resource	Primary Function	Priority Level
Magnetite	Depth modules and vehicle upgrades	High
Aerogel	Advanced crafting and base modules	High
Copper Ore	Wiring kits and core power systems	Medium
Table Coral	Computer chips and basic electronics	Medium

Store these items in wall-mounted lockers inside your submarine or main base before embarking on deep exploration routes.

Handling Hostile Aggressive Fauna

Hostile leviathans in modded biomes often feature increased movement speed and detection ranges. Direct combat risks destroying your vessel, so rely on evasion and defense systems instead:

Maintain Vehicle Energy: Keep vehicle power levels above 40% at all times to ensure defensive systems and thrusters remain operational.
Use the Perimeter Defense System: Trigger a non-lethal shockwave when predators approach to break off their pursuit.
Cut Engine Heat: If a hostile creature spots your vehicle, disable the engine immediately. Reducing your heat and noise signature helps predators lose interest faster than trying to outrun them.

Upgrading Vehicle Depth Modules

Descending past 500 meters without adequate hull reinforcement leads to rapid crush depth damage and vessel destruction.

Always keep a repair tool and extra Titanium in quick-access storage to fix environmental chip damage immediately. Upgrade to MK2 and MK3 depth modules as soon as blueprints and materials become available to safely access deeper, resource-rich biomes.