20-Year Prospect
Athletes aren't built to last. Ask anyone. An athlete in their thirties is unconscionably old and is probably gearing up for retirement. Sure, there are a few who edge on into forty, and in extremely rare cases beyond that, but for the most part, there's a hard cutoff. What does this mean for you? Athletes have a second act to their lives.
Sports are less a career and more of something you do until your body inevitably breaks down. After that, if you can get a job coaching or commentating—both fields with far more applicants than jobs—you can use that knowledge you gained in the pool. Otherwise, it's time for something completely different.
Jobs for athletes are growing more slowly than other fields (source). That's including ones people actually watch, like football, basketball, or soccer. Water polo is not the most popular sport out there, and most people think of it as exclusively Olympic. It's not, but that's the perception.
If you're playing professional water polo, it's probably for FINA (source), and you're on Team USA. Congrats. You are one of the extremely few lucky ones. There aren't any new jobs on that team, are there? Just a finite amount of spots, and if you get badly hurt or just aren't performing up to snuff, you're gone.
At least the sport itself isn't going anywhere. Water polo might not be popular, but it does have some hardcore devotees. You'll be toiling in obscurity for not much money, but you'll at least have fans.