The nereid from The Hidden Shrine of Tamoachan has a special feature called "Shape Water" (not to be confused with the shape water cantrip), which does the following:
Shape Water. The nereid can cast control water at will, requiring no components. Its spellcasting ability for it is Charisma. This use of the spell has a range of 30 feet and can affect a cube of water no larger than 30 feet on a side.
The control water spell can create a whirlpool, which is a 50 ft x 50 ft x 25 ft vortex. The vortex also pulls stuff in the water within 25 ft of it.
Whirlpool. This effect requires a body of water at least 50 feet square and 25 feet deep. You cause a whirlpool to form in the center of the area. The whirlpool forms a vortex that is 5 feet wide at the base, up to 50 feet wide at the top, and 25 feet tall. Any creature or object in the water and within 25 feet of the vortex is pulled 10 feet toward it.
When a nereid creates a whirlpool with this feature, does the vortex pull stuff from the water within an additional 25 ft, even if this "affects" a volume of water larger than 30 ft on a side? Does this depend on the size of the vortex?
If all of the water affected must be within a 30 ft range, then does the nereid get pulled into its own whirlpool?