Upper trigram
☵
Water · Kan
Danger and depth.
FamilyMiddle son
ElementWater
Hexagram 29 of 64
☵☵ The Abysmal
Repeated danger; keep your footing.
Lower trigram
☵
Water · Kan
Danger and depth.
FamilyMiddle son
ElementWater
The image
Water above, Water below.
Water over Water: danger and depth meeting danger and depth.
That combination is the whole meaning of hexagram 29. Nothing about it is arbitrary — change either trigram and you get a different hexagram with a different reading, which is why the 64 form a system rather than a list.