Helanca is a pique fabric with a four way stretch, usually made of Polyamide (Nylon). It is similar to Spandex and can be used in swimming and bathing suits, or other garments which require lots of movement and other technical performance needs. This makes Helanca clothes useful for many water sports, if you can still find them.
Only drawback is that if the fabric gets damaged it can run a line and unravel.
A drop of superglue applied in time can stop that.
Helanca is a highly elastic polyamide filament yarn developed by Rudolph Kägi in 1931. As the head of the American subsidiary of Swiss company Heberlein & Co, Kägi initially worked on the smoothing of surfaces for fabrics made of artificial silk. The result was acquired by his employer who developed it to the product maturity and patented this procedure. Helanca is a protected brand name.
Today, instead of the original artificial silk, only synthetic fibres made of nylon (polyamide) are used. Helanca swimwear, pullovers and sportswear were very popular in the 1970's, but got later superseded by Spandex.