I saw a lot changes, but they weren’t game breaking.
None of them made ships that can survive the whole battle in the previous update, almost always die in 5 minutes in the new one.
Most of the changes made in early bluewater naval were incremental and somewhat based on how things actually might work. They made HE shells a bit weaker, they made unwatering slightly faster, they made armor plates breakable but only by the highest caliber guns, etc.
Slow progress with time to test each change and all the changes were mostly adding things to the gameplay. There were most likely bad changes but there weren’t any catastrophical ones.
They did make changes to lower survivability, but again, they mostly weren’t that big.
Barbette fire was genuinely a decent change which managed to raise the importance of quick damage control reaction and managed to introduce weak spots to ships which were almost unsinkable before. Yes, a change to lower survivability, but a good one, and which did not break any core game mechanics and which, if anything, improved naval balance overall.
One of the bigger ones were to hull destruction. First iteration of compartment destruction was disliked but realistically it affected your game only after a great deal of time (> 15 - 20 minutes), considering that at the time there was no constant bot HE spam.
Second iteration of hull damage was EXTREMELY BAD at first. The Yamato could be sunk in a few minutes by light HE spam hitting nowhere near the waterline and without ever penetrating the belt. But community (literally every active voice in naval, both EN and RU) actually managed to talk gaijin into raising HP of hull sections and I do think that currently this system is very much useable, THANKS TO PLAYER INPUT, AND ONLY TO IT.
Right now gaijin basically does the same thing as they did with the second hull HP change, but they decided to not listen to the community. The change WILL result in the biggest BBs dying to small HE spam in a matter of minutes, just not due to hull break, but loss of crew through secondary guns and some AA mounts. Although the result is the same - ship sinks in 5 minutes.
Good luck I guess.