To start with, you'll need a fishing rod. Like all the other equipment, you'll find the blueprints for it in the Space Anomaly. It's a multi-tool upgrade and can be bought for 1 nanite, and this also unlocks the recipes for baits. Next, the exo-skiff. While it's better to fish from the top of your ship (once you have aqua-jets, off course), the exo-skiff provides incredible fish storage, doubling the size of fish stacks, and just plain looks cool. It is purchasable in the Space Anomaly as an exosuit upgrade, and once purchased and installed can be summoned like other exocraft, but only in bodies of water. Finally, you will need aqua-jets. These are purchasable as a starship upgrade, once again in the Space Anomaly, and simply allow you to "land" your ship on water. This means you can not only fish on top of your ship, but can get out into the middle of an ocean without 5 hours of swimming. Once you've done all this, you should make bait. The easiest is meal worms, crafted from condensed carbon. However I would also recommend using processed meat as bait, as it has a 40% rarity buff, and it can be crafted by running animal meat through a nutrient processor.

Once your equipment is ready, you can head to any body of water and start fishing. It's best to fly your ship out to the middle of an ocean, fish on top of your ship, and stuff your fish into the exo-skiff when you run out of inventory space. To get fishing, just attach bait to your rod, and cast. You'll see fish gather around and nibble at it, and eventually they'll latch on. If you're using a controller it should start vibrating but there's also a visual cue of the line turning green. Just hold down the same input you used to cast once this happens, and you'll catch your first marine animal! It may be different on higher difficulties, but I found the timing to be very forgiving, so don't worry too much about botching it. All that's left now is to relax and catch some fish!