Naval Mines in Claiming Cosmos: hidden mines unlocked at Armory 4. Placement, arming, and who they hit.
The honest weapon of a dishonest harbor. You do not see it until the hull does.
Place from water, not the land menu. Unlock at Armory 4. Arms after 10 seconds. Hits enemy Warships, Marauders, Tenders, and transports. You and teammates see them; enemies do not. Max 3. Trade ships ignore them. First $250,000, then $500,000.
Back to the building list or pick a map like Sol System and play Claiming Cosmos in the browser.