General thoughts

Hydro Bounty is likely the biggest Ninjago vehicle of 2021 and one of the biggest overall. The set consists of big carrier-like ship, 4 mini-vehicles and 10 minifigures. It looks great, offers great playability - though there are minor flaws that do reduce the final score.

The building experience is solid. The hull involved some nice construction tricks (windows, expandable side-wings, engines overall) which I did enjoy. Smaller vehicles are very simple to build. The whole set is supposed to be age 9+, but my 5 yo actually did a significant amount of the work and had little trouble.

In terms of parts, this set is a decent source. The hull foundation pieces would be useful for virtually any vehicle one could imagine, a significant amount of building bricks is also present (some Ninjago sets seem to be composed mostly of weapons or decorations, this has only some, proportionally). The price per part seems high, though. Perhaps that's because there are 10 minifigures in this set. Also, it doesn't have any small filler bricks that Lego Friends tend to have too much.

The ship is also great for display in my opinion. With little swords or other blades visible it could nearly pass as a generic sci-fi submarine. It's large and looks well from any angle. Extended engine plates make it seem even bigger than it really is.

Durability

Durability is a very important factor for me, as my 2 KFOLs (aged 2 and 5) tend to quickly discover any structural flaws in any Lego set they put their hands on (in other words - they reduce it to a stack of bricks).

The water chariot breaks very easily, but is easy to fix, too. Mini-subs' cockpit door breaks easily, otherwise they are solid.

The Hydro Bounty itself behaves well overall. The ship is reasonably solid, for its size -better than expected. It can be picked up by holding it nearly everywhere. Plates on its side add a level of structural integrity, though the smaller elements do fall off if squeezed too hard.

The set's elements have some flaws, though. The removable ceiling at the back required strengthening and was also one brick too low. So not only did it break all the time, but it was also too small to fit the figures inside the ship. Adding a strengthening layer was actually a necessary improvement.

The engines break off easily - they are connected by 2 technic pins each, which is not strong enough to hold them firmly. If you pick up the set you can notice both engines tilting down slightly. Also, the back hull that holds the brick is kind of fragile, so if you put the ship down starting at it's back, the entire ship's back-top side will separate from the back-bottom side.

The detachable robot from the front of the ship is the biggest flaw. It often breaks when you straighten its arms. It is also nearly impossible to attach the robot to the ship without breaking it. If you hold it just strongly enough to attach it, it's sides break, and you have to repair them, which often causes the robot to detach from the ship. I just stopped attaching it at all.

Playability

There are 10 minifigures in this set. That's a lot. OK, 2 of them are the robo-Wu's, so perhaps they're not "real" minifigures - but still, the value's there.

The ship provides lots of ways to play with. Sub storage compartment was also used as a prison, housed various other smaller sets, transported treasure, perhaps much more I did not see. The bridge holds 3 figures, one steers the ship, two help. There were battles for ship's control on that bridge, struggles of epic proportions ;) With expanded engine panels the ship can fly. True story.

Conclusion

With high value comes high price - or something like that;) I bought this set having mixed feelings, but I do not regret it at all. It's one my favourite right now, right behind Jay's Storm Fighter (70668).

If you can afford it, I sincerely recommend it. With all its flaws it's still one of the best sets in the recent years. It's a remarkable construction and has a great playability value.

I subtracted 1 star from playability for the durability problems. Value for money - I would prefer less minifigures and more bricks, but that's a personal preference of mine.

(Bonus - some work in progress pics)