Land and water never mix for movement. Subs are sneaky missile boats, Sea Shadows and Cutters rule surface water, and Radar and anti-air decide who gets to sit on the coast.
At a glance
Two worlds
Land vs water — never cross for pathing
I-400
Sneaky, long missile/torpedo reach, must surface to shoot and gets lit up after
Surface boats
Sea Shadow (heavy gunboat) & Cutter (rapid patrol) trained at the Boatyard
The coast
Pens and slips spawn right on the shoreline — lose the beach, lose the navy
Land and sea
Land and water use different units — subs must surface to fire; boats stay visible on the surface. Control the beach to train and support both.
What each hull does
An I-400 is the only stealth unit. Submerged it's almost invisible but still scouts about 8.0 tiles; it torpedoes other subs and missiles everything else at long range, but missiles plink buildings and HQs for a fraction of their raw damage — a full Sub Pen needs the better part of a minute uncontested to drop an HQ. A Sea Shadow is always visible, durable (240 HP), with a deck gun that feels like a Maus at sea. The Cutter is lighter (175 HP), faster (148 speed), and carries 5 quick-firing shells. Both restock at HQ, Workshops or owned depots — land cannons can't hit them, but anti-air can.
Seeing and being seen
You need Radar to fight a submerged I-400 you can't see. Radar lights enemy subs at long range for a short window, and a sub that fires lights itself. Slide I-400s along the waterline offshore near the enemy HQ, focus the HQ, fire, then move — anti-air will answer if you linger. Move a Sea Shadow or Cutter along the beach to hunt surfaced subs and rake coastal buildings while Maus and AT hold the land so the coast stays yours.
Bring Radar before you commit to a naval fight you can't see — without it, a submerged sub outranges and outlasts a boat.
Boats screen water while tanks and infantry hold land — they're a team, not a replacement.
Owning the beach
Both the Sub Pen and Boatyard are coastal — they spawn right beside the HQ on the waterline. If the beach is enemy territory, your new boat or sub spawns under fire and the enemy parks missiles offshore for free. Keep a little land force near the coast. New buildings block land paths the moment they land, but never water — use that to shape lanes while keeping sea lanes open.
Coast vs land
A Sea Shadow or Cutter can sit just offshore and harass buildings while your Maus hold the beach. An I-400 must surface to missile, so it needs that beach held even more. Lose the land and you lose the water — don't let the enemy walk a Maus onto your slip.
Coastal & naval warfare — Field Guide — Operation Brightwater