Only in pollen producing gymnosperm & angiosperm is the gametophyte life stage miniature, mobile & independent of water; the grain of pollen is the whole male gametophyte.
The multicellular pollen travels by wind or pollinator to the female gametophyte in the cone or flower for fertilization (without flagella). The pollen's freedom to travel away from water increases the chances of sexual recombination in sessile plants. Plants are no longer resticted to the distance flagellated gametes can swim through a film of water because the pollen grain delivers the sperm nuclei by pollen tubes to the ovule inside the flower's ovary or under the cone's scale.