five features in a well-designed lego set

The Triwizard Tournament: The Black Lake (76420) (Harry Potter theme) contains five features that typify a well-designed Lego set:

1. Miniature world. The set represents a miniature world, creating a level of immersion not found in other types of sets (e.g. sculptures)¹.

2. Simplicity. A relatively small number of pieces (349) are used efficiently to communicate a lot about the environment being modelled. The floating effect, for example, is simple but effective.

3. Minifigures. A range of characters with different characteristics are creatively captured within (broadly) the constraints of a minifigure. More detailed praise of the minifigures in this set is available here.

4. Configurable. The set is configurable and thus multi-functional (pictured).

5. Underwater theme. Sets with an underwater theme, like this one, are often the strongest. This includes the famed Lego Aquanauts (example pictured).

It transpires that the model fits into an acrylic display case (24 x 14 x 12 cm) such that only the above water section is exposed when the top is removed (pictured). This allows for the boat accessory to be balanced at an appropriate height, and film positioned on the sides of the case to create the illusion of water for the underwater component.
This adds a practical element prior to photographing and editing (using GIMP), and creates a reasonable real-world effect short of filling the case with actual water.