They have needed water for a long time. This episode they go and get it, and it turns out to be almost embarrassingly easy. The rest is a farm, a shortcut home, and the usual lesson about gravel.
Into Drizzling Cove
Basket grabs some coal, there is a bad dad joke or two, and they head into Drizzling Cove, emeralds 17 through 19. Water is visible almost right away. So is an enderman, who gets angry, and has to be killed while one of them is busy crafting a bucket.
A minute later they have a water bucket. That was easy. We should have come here a long time ago. Yeah, we probably should have.
Up the waterfall
The cove fights back with creepers coming down the waterfalls and a lot of mobs pathing toward them from every side. One of them suspects they did something wrong at some point and are being punished for it. A skeleton seems to have a Punch bow. Someone thinks the top of the waterfall must have something cool. Do you want to go for it and die?
They swim up anyway, the fast lane, as one of them puts it. At the top is more level, a lit cave, and across the water a little island house with flowers around it. In a chest along the way they find a new kind of blaze rod: Sharpness I, Knockback II, Fire Aspect II, Looting I. They agree to keep it safe in a chest.
A secret ladder shaft
Then a secret tunnel with ladders in it, and gravel. The gravel turns out to be for a deep hole: drop gravel, put ladders on it, and climb down. One of them falls, places a ladder mid-fall, and catches himself. A new way to fall safely, as long as you have a ladder in your hand. The shaft comes out by the lava area, near the entrance to the water area, and gives them a shortcut back.
A farm at last
Back at base the water goes down, and the plan is an infinite spring. The melon tracks come out and seeds and carrots go in. One of them has Kiss the Girl from The Little Mermaid stuck in his head and does not know why. They admit they thought the water level would be much harder, with guardians, since its emerald numbers were higher. You could almost see the water from where they stopped last time.
There is also an iron sword handoff: one of them is down to a stone sword with two attacks left, and the other gives him one of two half-broken iron swords. Man, you take such good care of me.
Fifth map together
Back in the cove they clear the area around the island before visiting it. The house has a jukebox, a chest in a tree, and a floor that one of them is nervous about. Rightly. There is gravel under the chest, and it releases a rapid dispenser of silverfish eggs. What is this, our fifth map together? I'm never going to learn that lesson.
The loot is a fishing rod with Lure VIII, lots of redstone and lots of wood. At the end they pillar up the waterfalls, find a guardian spawner in the water, and take it out together with a gold pickaxe.
