This is something I never knew I needed, but now that I've been shown the error of my ways, I've definitely needed the Kljunari all my life. I plan on introducing these cute little guys into my campaign setting the next chance I get. The inclusion of NPC stat blocks really puts this product high up there when in comes to usability.
As a player option, you can tell a lot of heart went into fleshing them out as a believable race for 5e. From the flavortext, to the lore tidbits, to the mechanical side of things, it's all very well executed. The Kljunari have a healthy mix of situational and general racial abilities that allows the player to feel great in a water-based setting, but not feel underpowered outside of water. It's a good balance!
When next I have the chance to make a PC, I'm going to pitch this race to my DM. With luck, I hope to come back with more detailed feedback on how the Kljunari plays in a live scenario -- but either way, I'm excited to try it out and I can't wait to toy with these guys soon!