I have a circa 1940 gardening book with instructions for creating a pool
from sheet lead.

The abutting sheets are to be crimped at 90 degrees, one with 2 inches
overhang, the other with 1 inch. The longer is folded over the shorter,
then both are bent over and soldered along the seam. The pieces are
joined together in that manner into larger sections representing bottom
and sides, which are crimped together and soldered.

Can sheet-lead still be purchased? Would the lead surface oxidize over
time, as in pipes? The book says this will not harm fish, so I assume
either they're are lying, they never tried it, or some sort of patina
develops to prevent lead leaching into the water.

The book says copper can be substituted for lead, but from what I've
read this would also unhealthy for the creatures living in it.

What are your thoughts?