Why is dna replication describe as semiconservative

Semiconservative DNA replication is a mechanism of DNA replication which results in two copies of DNA, each consisting of one parental DNA strand and one newly synthesized. Each strand of DNA helix serves as a template for new strands. The new strand remains associated with template strand.
Oppositely, in conservative DNA replication, each strand of DNA helix serves as a template for new strands, but new strands separate from template strands and associate into new DNA, so one DNA copy has both original strands, and another one has both new strands.

The zone your looking for is the intertidal zone.

Dthrough a slow process