Sailors.

The two shipwreck sailors looked at the group of beautiful, half-naked women with hungry eyes and delight.

They had no idea that the island was protected by a jealous female goddess who turned all male Invaders into beautiful women and ensured that the babies conceived on the island were female, thereby preventing them from altering the delicate balance of power. 

The transformation would not begin for another 24 hours, and by that time, every girl would have had their time with them and hopefully gotten pregnant by them before they turned into women waiting for the next shipwrecked men to appear.