Water flow and renewable sources
A source flows down first, spreads up to seven blocks horizontally, seeks nearby drops and respects obstructions. Flows drain when the source disappears. Adjacent water shares surface corner heights instead of rendering every sheet as an independent horizontal shelf.
To make a renewable 2×2 pool, dig a solid-bottomed 2×2 basin and place sources in opposite corners. Let the other cells become sources. Collect while keeping the remaining sources able to regenerate the missing cell. The regeneration rule requires two neighboring sources over solid ground or another source. A lonely source or an unsupported arrangement does not qualify.
Fluid updates use a 0.25-second interval with up to 384 queued cells per interval in loaded chunks. Unloaded work waits. Large floods therefore settle gradually.
Buckets and the well
Collect source water with an empty bucket; right-click a surface with a water bucket to pour. Only wooden water buckets are drinkable. Hold right mouse into open space, or R, to drink. Copper, iron and steel water buckets collect/place water but cannot be drunk. Direct source drinking remains available.
Cow/goat milk stays drinkable from every corresponding bucket material and cures poison even when you are fully fed and hydrated. Drinking returns the correct empty vessel.
At a settlement well, right-click the winch/rim/rope area with an owned empty wooden bucket. Its lowering cycle takes about four seconds. It produces water only if the well still contains real water at completion; a dry well returns your bucket.
Lava
Lava is luminous, damages living bodies, flows slower than water and spreads three blocks horizontally. New worlds have deep pools and occasional ceiling-fed falls. Only empty iron or steel buckets collect a lava source. Wood and copper cannot.
Right-click a surface with a filled iron/steel lava bucket to pour. Water touching lava makes obsidian for both source and flow contacts. Do not assume another game's different cobblestone/source mixing rules apply.
Rowboats
Select a rowboat and right-click clear water to launch. Right-click it to board, WASD to row and Shift to leave. It accelerates, follows the water surface and collides with banks. Left-click to recover one rowboat item. Approximate rowing speed is 4.2 blocks per second. Sitting/boating still uses hunger and hydration in Mortal.