The plot itself is quite good, the conflicts are intriguing enough too keep me interested. The gap between the cuteness and dire situations feels just right. You'll find quite amusing ship crews here, and each with their unique characteristics. For me, all of them are likeable, and the entire crew get their screen time, some even showing character development, though it is not much. Of course some people will complain about how useless the adults here, or not so fond with loli solving everything, my advice is: look at the trailer or synopsis before watching, there are absolutely no reason to watch anime like this if you are allergic to cute girls.
The best part of Haifuri is, the ocean battle! yes, this show is about battleship voyage after all (though it's supposed to be peaceful class training). Without spoil too much, the girls ship will face various type of enemies. And it's not about which one has the best weapon or bigger ship, various tactics will be involved, that's because our protagonist ship is not the best here. There are also other problems presented that might happen on the voyage (I'm not expert in this part, as people of the land), like lack of supply, etc. which bring more variety other than battle, and there also relaxing moment for you to feast at moe and cuteness.
To summarize, this is quality anime which might be underrated. It's recommended for anyone who like action but bored of shonen anime, because this one will be cuter. Of course if I want to nitpick at some plot hole or weird situations it might lower the fun while watching this, but why would I? 10/10 for the enjoyment
