lagoon
潟 centers on a shallow coastal body of water partially separated from the sea: a lagoon.
潟 combines 氵 (water) with 舄, which likely contributes the sound and the idea of a marshy or saline flat. The exact historical development of 舄 is uncertain.
Water 氵 beside the unusual shape 舄, which looks like a mortar 臼 over a fire 灬, suggests a shallow basin where water sits: a lagoon.
For セキ, imagine a lagoon so still it reflects the sky like a mirror: the reflection is a 'second sky' -> セキ.
Niigata (city, prefecture)
lagoon
tidal flat; tideland
Niigata University
Albirex Niigata (professional football club)
Lagoon Nebula
Niigata University of Rehabilitation
Niigata Chuo Bank, Limited
Niigata University of Health and Welfare
Niigata University of International and Information Studies
Niigata Institute of Technology
Niigata Industrial University
Niigata prefecture (Hokuriku area)
Chūetsu earthquake (Niigata prefecture, 2004)
University of Niigata Prefecture
Niigata College of Nursing
Niigata Prefectural Museum of Modern Art
Niigata Prefectural Police (abbr)
Niigata University of Management
Niigata University of Pharmacy and Medical and Life Sciences