text:  This is Science Friday. I'm Rachel Feltman. I'm going to go out on a limb and guess that a good chunk of you listeners spent at least a little bit of your childhood dreaming about becoming a marine biologist. Personally, I had this whole schedule drawn up where I'd work at an aquarium a few days a week and then go to space for the rest of it. But even folks who commit fully to studying life in the sea face a lot of barriers to entry in this highly competitive field.