Money is no small matter in Aquanox, and you’ll want to stockpile a decent store of credits if you plan to purchase the latest weapons and sub upgrades. Making money in Aquanox isn’t complex, but you’ll need to be a thrifty spender if you don’t want to find yourself drowning in debt.
Money in Aquanox is earned by completing side-quests, bounties, and by selling materials.
The easiest way to make money in Aquanox is to sell off materials. These are everywhere in the deep blue sea. Dead enemies can drop them, but the purple gears indicating scavenging locations on your sonar have the most materials, and are more frequent. Now, that said, I don’t recommend selling off materials unless you are near the storage cap or are in a bind. You need those materials to craft ammo, armor and shield packs, and to upgrade your sub. Materials may be the easiest way to turn a buck, but don’t rely on them for this purpose.
Instead, visit every dock you can and complete whatever side-quests and bounties are on offer. You can earn some decent equipment from them, but you will always earn some substantial cash in Aquanox by completing them. The further into the game you are the more money you’ll make, and you can double-back at any time to find side-quests and bounties you may have missed.
Do keep in mind that you won’t make enough money in Aquanox to buy every single sub upgrade and duplicate weapon in a single playthrough, so you’ll need to spend your money in Aquanox wisely. You can bank a bunch of credits, so save them for the upgrades and weapons that matter to you, otherwise you’ll find yourself at the end of the game a Jack-of-All-Trades, without a single sub ready to rock the final encounter. Trust me, you don’t want to be in that position.