While visiting the springs of Florida a couple years back, we noticed these circular holes dug in the sand virtually everywhere. Upon closer inspection you'll find a single fish, the nonnative Blue Tilapia chilaxing in each crater. The males dig these holes and spend all day maintaining their shape and protecting them from other aggro bros in hopes of attracting a female. It's sort of like showing a picture of your penthouse apartment on your Tinder profile...kind of. If a female is intrigued she'll join him for a quick romp in the sand, release her eggs to be fertilized, and then quickly suck them up into her mouth where they will develop for the next three weeks. During this time she will occasionally let the babies leave her mouth to explore, but if danger approaches they will quickly return to the security of her mouth for protection. For us land dwellers we might call this behavior "eating your children," but for fish it's totally normal and called "mouth-brooding." They use this parenting strategy to increase the survival rates of their offspring much like we humans protect our kids from potential danger while they are young.