This will be a guide to get all 6 new achievements in the aquatic update in about 5 minutes of actual work, along with an hour of idling. In the main menu, press play and create a new tutorial world by selecting “play tutorial”. Upon starting the world, you will need to walk forward a bit and press “B” every time a tutorial box appears to skip it. Open the inventory and eat the meat to regain full health. Keep walking straight ahead for a while until you reach a giant diamond pickaxe. When underneath it, turn left and head up the stairs and through the gate. There is a chest there, grab the raw cod (fish) from the chest and head back to the pickaxe. Now turn left again upon reaching it to go to the new aquatic bit from the update. Before you do there should be a few little houses on your right hand side; acquire a bed from one of them. Now, keep walking straight ahead and jump in the water. There are a few trampolines in the water, with dark green dried kelp blocks next to them. Get 1-2 of these blocks (you destroy them quicker when you are not in the water). Afterwards, dive down to get some kelp leaves (long vertical plants) as well as feeding the raw cod to one of the many dolphins swimming around to unlock ECHOLOCATION.
Next, we will need a furnace, which can be found on the right hand side on the shore, looking in the direction you came from. In this furnace, place the kelp blocks as fuel and the kelp leaves as ingredient. This will unlock alternative fuel. Now wait for a kelp block to dry and retrieve it, to allow you to eat it. From now on, don’t eat anything else but dried kelp leaves, as your 3 full days of idling for CASTAWAY have started now.
Next, we will create the conduit, by heading to the center of the lake. Grab the all items from the chest. Open the crafting table located in the floor next to the chest. Go to the “Mechanisms tab”, in here go one square to the right and then one down to find the conduit (beneath the beacon). Craft it. Next, head into the center of the water here, right beneath you, there will be the conduit set up ready. Place the conduit on the wooden block, then remove the wooden block with the axe you got from the chest. This will unlock MOSKSTRAUMEN.
With the axe still in your hand, head to the bottom of the lake to find 4 seapickles (green plant with a blue bit at the top). On various spots there are already 4 on one block, if destroying those with the axe, you should be able to pick all 4 up pretty quickly. Place 4 of them back on a single block on the floor to unlock 1 PICKLE, 2, 3, 4.
Now head back to the conduit, sit right next to it and let your console idle for 20 minutes to unlock sleep with the fishes (unlocks after spending 20 minutes under water). The remainder of the time you can partly skip by sleeping (during nights and thunderstorms) (unlocks after eating nothing but dried kelp leaves for 1 hour, reduced by the amount you spent sleeping). CASTAWAY
Grats on your completion!