Because the move through water
There is a spectrum of electromagnetic radiation with variable wavelengths and frequency, which in turn imparts different characteristics. ... X-rays and gamma rays have the same nature as visible light, radiant heat, and radio waves; however, they have shorter wavelengths and consequently a larger photon energy.
I always thought that 'polygamy' refers to the social system in which a man
may have more than one wife, and I thought there's some other word for
where a woman is married to more than one man.
But when I went to look it up just now to answer your question, (which by the
way you could also have done very easily), I found a definition that says it's a
"state of marriage between many spouses". That doesn't specify genders, so
I guess it means any marriage that involves more than two people, no matter
how the genders may be represented or distributed within it.