Introduction: Hillbilly Jacuzzi
Little garden pond, that is cool in the summer and warm in winter. 4-5 people can sit into it, heatable in winter.
Step 1: Choose the Best Place
Some place where it is not too steep, and there are enough bushes, so that the neighbours cannot see you. Maybe nice view to the landscape.
Step 2: Start to Dig
After you cut off all bushes and grass at the surrounding area, you can start to dig. The lake was made in the beginning of winter, it means that we could not dig in the morning. So usually only the top 30cm (12 inch) was not frozen in the afternoons. Between each layer we had to wait few days until the soil was melting enough on the sun. Be prepared that there might be many pieces of roots in the beginning (take branch cutter and saw).
Step 3: Put Some Concrete Blocks and Stones to Hold the Weight
People and the water are heavy, to make sure that the ground will not deform under the weight, I've decided to collect some concrete blocks and stones. About 4 people can sit in the water comfortably, I hope they will have enough space for legs.
Step 4: Mud and Clay
To form some nice shape you have to put extra inches of clay and mud on the inner side. Sometimes stones or bigger chunks of the soil are missing, these gaps had to be filled. Be sure that you dig deep enough, several inches deeper, because of the extra needed layers. The clay can prevent the leakage if you might have some small gaps on the foil or tarp later.
There will be stones, collected from the forest around the pond, so be sure that the surrounding area has to be to flat, otherwise the stones might roll into the water. They are preventing dust and mud washed into it too.
Step 5: Add Pond Foil
Measure the surrounding ground, because it should have the same height at every direction. I bought 3 x 4 meter (10 x 13 feet) of pond foil with 0.5mm thickness (it should be good for such a small lake, it was 25 euro). You can add optionally some tarp under the foil, for example I did. Place some stones temporarily inside the lake, because the wind might take the foil until you fill it with water.
Step 6: Hide the Sides
You will need some extra ground, honestly, during digging I could collect more, just I didn't know that so much will be needed for hiding the sides (Also, it's better to dig deeper at the surrounding area). For horizontal measurements, I used a metal tube.
Step 7: Water Heater
You need a method for heating the water on fire, I used an old iron barrel, few bricks, a pump and few plastic tubes (be careful, they might melt). I could see many methods on the internet, but since I know that hot air, smoke and fire are moving upwards, I realized that puting the barrel to the top is the most effective way of heating water (make it simple, it's like cooking). Next day morning, the top of the lake was totally frozen, to heat it up to 30 degree Celsius (86 F), it could take 3 hours (the water volume was about 1.5 cubic meter, so 1500 liter).
Step 8: Let's Try It!
Even if the water seemed to be totally clear, some ground was continuously falling to the water, because of the small waves that I made. Later it became very brown. You would need much more stones on the side to prevent these falling pieces.
Step 9: Summer
Actually 4 or even 5 people could comfortably sit, or 2 of them could sank totally under the water meanwhile. The water was easily became hot on the sun, around 40 degree C (104 F), so next time I was hiding it under another tarp to keep it cold.
Step 10: Mistakes, Improvements
After 6 months the ground around the lake was slowly deforming and losing the measured shape, so some later fixes were needed. When the bushes started to grow leaves, they also started to grow strong roots, so I could feel that some of them are about to make holes at the edges of seats. I would use an extra little bucket just for washing legs and preventing the muddy appearance.