Note: As of 1.5 water will now form sources over itself properly.
"Hole In the Ground" technique
This is the most convenient way to create a two-block-deep lake. It's perfect if all you want is a little surface of water. Note: that the deeper the lake, the less practical it is to dig it that way.
How To: Deep Lake w/ Ease
You can make a lake any depth with ease! All you do is dig out your lake. (i.e. 6 blocks deep and also a rise near the edges) Then you do 1 layer of dirt where you want the water level to be. Fully cover the lake with the one block high layer and fill/overlap with water. (Make sure water becomes fully still/settled!) Grab a diamond shovel and with ease you dig up the top and only layer of dirt as your lake fills with water. You can also add to an already made lake like this, and just add 1 layer of dirt blocks at water lvl and watch as the waterfall extends over your extended lake. Once again you dig out the layer of dirt once you've gotten the water to settle.
First, dig a one block deep hole and fill it with water. The size of the hole is irrelevant, as is its shape. You're already almost done, make sure there are no currents ruining your fun and then dig one block deeper. The springs of the first layer will fill whatever is under it.
If you listened, you should already be done, but let's say you want a three blocks deep lake. You dig again, however you should note that under water you do everything at a slower pace. The bigger and deeper your pool, the more it will be a pain to dig.
What you need to understand about water is that it can't create springs if there is no block under the would-be spring. That's the reason why lakes don't fill themselves when one infinite spring is placed up-stream. However, water floats as of now in Beta, and if there's a block between two floating springs, a new spring will be created. That is the basis of this technique. Both versions are viable, but this version is the most efficient block wise.
The deep pool needs more preparations. First you need to dig your pool. Make sure there are no holes in the walls where water won't be directly above, this will cause currents and the point of all this is not to get currents
Secondly, set up rows at the first layer of your lake, one block large, two blocks deep (the length is determined by your pool) and separated by two blocks of nothing.
= walls, = rows (or blocks you'll need to Destroy), = nothing, = water
Seen from above, the walls are as deep as your pool needs to be but the rows are two blocks deep
Next, place springs of water all along the sides of the rows. You're ready for the next step if you have a layer of calm water separated by rows of dirt or whatever you choose to use.
The will become water in this schema
Finally, destroy the rows from the upper section down. This is important, if there's no block under, the new water spring won't form.
Here seen from the side
With the upper row gone, a water spring is formed
The top are in fact water springs, the rest is water coming from those
Now you are done! Enjoy your lake! Notice that the schemas only represents the pattern you need to replicate, the size of the pool doesn't matter. As demonstrated in the schema, you don't need the side of your lake to be even, you just need to make sure every row you make is surrounded by at least two springs of water.
Deep Pool 2
This new version is a mash up of the two techniques above. The two versions are viable, however some may find this one more simple.
First, dig your lake just like before. Make sure there's no hole without a water source above it directly and you're set to go.
= rows (or blocks you'll need to Destroy), = nothing (later it will be the water), or = walls
This is just a plain example of what the lake should looks like from the side.
Now, add a layer of blocks (dirt is best). The purpose of this layer is to receive a pool easily filled. It
doesn't need to must not be thicker than one block, you're just making your life harder if you do.
Notice the placement of the layer of . It is in only to stand out from the walls. This layer must cover all of your lake.
Finally, fill the one block deep pool you're supposed to have at the top with water, make sure it's all smooth and currents-less, then destroy the layer supporting it. If all was done right, you should be done!
Notice the that have turned into , this is your layer of springs, all that is left is to eliminate the layer under it. The lake will fill itself afterward.
Note that this schema is only an example, the size of your pool doesn't matter (except for the work you'll need to do).
So you want a lake filled with springs for whatever reasons? As always, I'm here to help. This is the best way I figured myself, if you believe you can share a better technique I invite you to do so in the discussion page.
Note; you should never apply any technique to the bottom of your lake if it's flat and full, just fill it with buckets, the self-replicating nature of the water make it easier on a flat surface.
Alright, as you probably know, we can't stack water springs on top of each other—they float. They need to be placed against a solid block first.
First step is, as always, dig your hole the way you want your lake. As always, make sure it's perfect and ready to receive water. Next, fill the bottom of this hole with water, this should be the easy part.
Now the harder part, which really is only time taking. Make a grid above your first level of water. It must surround one big square made of at most 4 squares of planned water.
Illustration of what your grid should looks like.
When your grid is perfect, you can start filling up. Start by placing water on the inside of the square (where the is on the schema above). When you're done with that part, replace every block in your grid by a spring of water. There's no particular way to do it that is best, but you must make sure to never, ever, isolate a block. You always want every block to be relied to another block so that you can put a springs in its place. If you goof, refer to the "there are current" section.
Now, to finish your lake you just need to recreate the grid at every layer until you reach the desired size for your pool.
Note, I said "at most" because, if you make a 3x3 square, one block will be out of reach for you to place a water spring. The shape of the grid can be modified to fit the shape of your pool if it's not a square, however, make sure you have a block to place a spring everywhere you need it.
This way works better if you don't actually have a lake yet—in fact if you do, you'll need to fill most of it in with dirt, except for the top layer. (If you don't have a lake or valley at all, you instead dig out the top layer, or at least a 2-block wide outline, 1 block deep.) Go around the edge of your one-block deep depression, and place water in an alternating pattern, like one color of a checkerboard. You should only need to go a couple of squares in—that is, every other space at the edge, and the alternating spaces just inside them—before the water springs multiply to fill your space. If you dug the two-block-outline, at this point you should dig out the interior and let the springs multiply over the whole area. Check for any missing springs and fill them.
Then, you dig out the next layer of your lake, or a 2-block outline. Again, place springs, but make sure to put them against the new floor. Again, finish digging out the second level of the lake, and let the springs multiply. Repeat for as many layers as you want—for deeper bottoms, you may need help to stay down there long enough to dig. Placing temporary doors is a "low-tech" solution, but can destroy springs—to fix that, on your way up, replace the door with two blocks of sand or dirt (plus one if you mined the block beneath it), then mine them from the top down. If you have a helmet with Respiration and/or Aqua Affinity, that can help a lot with deeper lakes. A potion of Night Vision can make it easier to see what you're doing.
Creative Mode or Silk Touch enchantments Only
Fill your lake with ice blocks. Place Glowstone blocks on top of the ice every two blocks away. Let the ice melt. Since ice blocks under water blocks turn to water, you only need to melt the top layer. Finally, destroy your glowstone blocks.
Ice is obtainable in survival mode with use of the silk touch enchantment on any tool.
"There are currents!"
NOTE: A current means there is no spring at the location it is pointing, so when we say "fill the current" we really mean "fill the empty block causing the current".
If there are currents, it's alright, you can fix it rather easily. Depending on the kind of lake you've made and the placement of the current, you should either:
1) Make a line of blocks at the water level and reach the current. When that is done, place a spring on the side to stop the current. Unfortunately, you will need to replace every spring you've eliminated by placing blocks. If you don't want to go through this hassle, you can place the line of blocks one level deeper and reach the current from below. A new spring will be created automatically above the new base you just created. Destroy the line and you're done.
2) If the pool isn't too deep, you can place a column of blocks that goes under the current, the water will automatically create a new spring to replace the missing one.
3) If it's an under water current, it means there's a hole in the wall or a stray block is blocking the water above this point. If it's a hole, fill it with either a spring of water or a block according to your preferences/plans. if it's a stray block, destroy it to allow the passage of water or if you want to keep a block there, fill the hole under it with water.
Swimming in a Lake
Sadly, there is a con to making lakes this way: while it definitively takes less time, the way the springs are placed will create a downward current. Swimming up in an artificial lake will take a lot more time because of that, however you can fix it by two ways:
First, you can actually fill the hole you made with springs. This will take some time depending of the size of your lake but it will be far easier to swim. I added a sub section with more info to do that in a faster way. See "Pure Lake".
Second, you can place one or more collumns of springs. While it will still look like a uniform lake, you will have access at a couple of sweet spots to swim up faster. The downside is that if your lake is a little too deep, you'll be dependent of those to swim up. However it will be very useful if you know exactly where you'll need to surface every time.
The represents only the springs. While the top layer of springs will drop a downward current, the column of springs on the right will have no downward current, thus it won't slow you if you swim upward.
Taking Water From a Lake
The water you see in your lake is superficial, what this means is that, contrarily to a regular pool of water one-block-deep, springs won't auto-regenerate. There's a set number of springs in the top layer of the lake, and if you fill your bucket with one of those, that spring won't be replaced naturally, you'll need to do it yourself by referring to the "There are currents!" section above.
If you want your lake to give you water forever, you can always fill the bottom layer with water, at this level, the water will regenerate eternally but you'll need to dive to get a new bucket of water.
If your lake is too deep or you don't want to dive every time, you can either dig a one block deep line that will go around your lake or build a new pool beside your existing one for your buckets need.
Alternatively, you can dig a 3x1 hole and fill it with water. You will be able to infinitely take water from the middle block. Also, you can make it 3x2 (or 2x2) and take water from all blocks.