Waterfall
A tsunami in the shape of a dragon flies off the cliff, then comes crashing down to the ground. This skinny tsunami of water flying down to the ground is a waterfall.
Can you see why a tsunami dragon (especially the Asian skinny snake-like kind) could be a waterfall? Try to imagine it.
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たき
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Despite how cool a dragon waterfall is, to be honest it's also pretty tacky (たき).
Now imagine it being a bit tacky. Dragons are alright but... you just don't want to overdo it, you know?