Approximately Up Submarine & Underwater Build

Somewhere past Earth and Moon lie ocean planets — worlds that demand a hull capable of space AND underwater travel. The full Steam release (August 6, 2026) ships with the Houston, We Have A Submarine achievement (1000 m below sea level), the Green Trench achievement (bottom of Green Trench), and ocean-planet objectives like Drop The Depth Diver and the legacy Fred’s Quest event. This guide explains how to build a hybrid space-submarine that handles vacuum transit, splashdown, and 1000+ m descents without flooding your cargo bay. Pair it with Power and Data Routing, RCS Thrusters, and the Achievements guide for the full submarine ladder.\n\n## Why submarines matter in the full release\n\nApproximately Up’s launch shipped with at least one major water planet in the route map, plus late-game objectives that reward hybrid builds. Demo players already had a preview through the Fred’s Quest event (April 2026), which required finding 24 eel eggs in an ocean using a submarine. The full release includes the Houston, We Have A Submarine and Green Trench achievements — both tied to depth and trench runs — and patch 1.0.007 added clearer in-game hints for both objectives.\n\nIf you build only vacuum ships, you miss:\n\n- Two Steam achievements (and the bragging rights for the Green Trench run)\n- Late-game mission chains that gate unlocks behind ocean exploration\n- Story content tied to Fred’s underwater arc\n\nThe good news: a single hybrid hull can serve both roles if you plan ballast, lighting, and depth-aware power routing.\n\n## Anatomy of a hybrid hull\n\nA submarine-capable hull needs:\n\n| System | Purpose |\n| --- | --- |\n| Watertight frame | Block-by-block hull with no leaks; build core, then close gaps |\n| Floodlights | Illuminate dark ocean depths (you start with 4 once Chasing Fire is complete) |\n| Battery pack | Power Floodlights and depth systems; solar panels barely reach underwater |\n| Atmospheric thrusters | Surface manoeuvring and descent control near coast |\n| Electric thrusters | Underwater thrust on most ocean worlds (water counts as fluid) |\n| RCS thrusters + controller | Orientation in low-visibility depths and trench corners |\n| Radar | Detecting eel eggs and depth markers |\n| Cargo bay | Sized for the eel eggs, mastodon, or treasure payloads |\n\nYou cannot bolt atmospheric and electric into a single thruster block. Run two parallel propulsion branches: atmospheric for the surface skim and descent glide, electric for the deep dive and bottom manoeuvring.\n\n## Step-by-step: build your first submarine hull\n\n1. Start with a standard Earth lifter layout from Build Your First Ship — flat frame, batteries, power router, joystick, seat.\n2. Enclose the frame in a watertight shell. Any gap floods when you submerge; trim holes for windows but seal cockpits and cargo.\n3. Add Floodlights — these are the bright searchlights that pierce deep ocean darkness. Mount two on the nose, two under the keel.\n4. Branch a second power line for the Floodlights so they don’t compete with main thrusters when you spike thrust. Use a power router for isolation.\n5. Add electric thrusters below the waterline (mostly under the keel) for descent.\n6. Keep atmospheric thrusters above the waterline for surface takeoff and skim.\n7. Add RCS thrusters at the corners — pitch, yaw, and roll in trench corners is brutal without them.\n8. Wire a Radar to your instruments and power it through a dedicated branch.\n9. Test in shallow water first. Drop a few hundred meters, verify Floodlights and orientation.\n10. Save the blueprint with B — you will rebuild at least twice.\n\n## Power management underwater\n\nSolar panels barely produce underwater. Treat the submarine as battery-only below the splash line:\n\n- Size battery capacity for total mission time + safety margin\n- Disable non-essential consumers during descent (Floodlights on reduced brightness, radar on long range only)\n- Switch off surface thrusters once fully submerged to save power\n- Bring a spare battery bay if the trench run is long\n\nFor comparison, see Solar Panels — those rules flip entirely underwater.\n\n## Depth discipline\n\nThe Houston, We Have A Submarine achievement requires 1000 m below sea level. Green Trench goes far deeper and rewards exploration at the bottom of an extreme trench.\n\nTips:\n\n- Descend slowly — momentum bleeds RCS propellant; pulsing electric thrusters on/off is more efficient than continuous burn\n- Watch the altimeter — community testing suggests underwater pressure at extreme depth can buckle frames that worked at the surface\n- Carry spare RCS — long descents rotate you hundreds of times; a depleted pitch jet mid-trench ruins a 20-minute run\n- Use waypoints — set radar markers before you descend so you don’t lose the trench mouth\n\nIf your frame shudders before 1000 m, redistribute weight (heavy keel) or add structural bracing around the cockpit.\n\n## Mission hooks: Drop The Depth Diver and Trial By Thrust\n\nPatch 1.0.007 added clearer in-game hints for both Drop The Depth Diver (depth challenge) and Trial By Thrust (thrust-meter challenge). Together they teach the dual ocean-vacuum loop:\n\n- Drop The Depth Diver — descend to a marker, retrieve a payload, return to surface. Tests ballast, power budgeting, and radar.\n- Trial By Thrust — long burn under water load, similar to Need For Thrust in vacuum but with fluid drag. Tests thruster count and battery size.\n\nBoth rewards unlock inventory parts that feed later hybrid hulls.\n\n## Co-op submarine play\n\nFour-player co-op splits submarine roles cleanly:\n\n- Pilot — fly mode, joystick, RCS commands\n- Engineer — power branches, watch battery meters, reroute if a thruster shorts\n- Navigator — radar monitor, depth tracking, mission objective readout (O)\n- Spotter — exterior view (if available) and Floodlight targeting on eggs/treasure\n\nDiscuss rewind policy (Press P) before a Green Trench attempt — losing all your eggs at the bottom because a teammate panicked costs hours.\n\n## Eel eggs and payload specifics\n\nThe legacy Fred’s Quest event (April 2026 demo) used 24 eel eggs of varying weight. The full release reuses similar payload diversity on its ocean planets:\n\n- Heavy eggs give more score when delivered intact\n- Smaller eggs are easier to retrieve from tight crevices\n- Cargo bay shape matters — eggs roll; add low friction or strap them down with cargo crates\n- Radar ping is your friend — eggs show as faint dots on radar at close range\n\nBuild a cargo bay with at least one 1.2 × 1.2 × 1.2 gate to use your standard mission gear.\n\n## Troubleshooting\n\n| Symptom | Likely cause |\n| --- | --- |\n| Floodlights flicker | Battery too small under load | Add battery capacity; isolate Floodlights on a branch |\n| Ship floods instantly | Hull gap | Patch with frame blocks; double-check cockpit seal |\n| Cannot reach 1000 m | TWR too low at depth | Add electric thrusters; trim atmospheric set |\n| Spinning uncontrollably in trench | RCS battery dead mid-run | Carry spare RCS; shorter bursts |\n| No radar pings | Outside trench radius | Climb slightly to confirm depth |\n\n## Related guides\n\n- Build Your First Ship — base hull template\n- Power and Data Routing — branch power for lights and thrusters\n- RCS Thrusters — orientation in deep trench corners\n- Solar Panels — why they fail underwater\n- Achievements — submarine achievement ladder\n- Co-op guide — split submarine roles\n- Missions Walkthrough — Drop The Depth Diver context\n- Patch Notes — 1.0.007 depth hints\n\nA submarine hull is the most fun you can have with Approximately Up’s wiring. Start small — a sealed Earth lifter with Floodlights — then iterate to a 1000 m diver, then a trench runner. Each rebuild teaches you which branch matters more: power, pressure, or payload.

Fred's Quest — submarine and ocean planet basics