What is the highest latitude when there are more than 0.518 square miles of water, a longitude less than -99.830606, and a population of 18?
CREATE TABLE "c" (
  "township" text,
  "county" text,
  "pop_2010" real,
  "land_sqmi" real,
  "water_sqmi" real,
  "latitude" real,
  "longitude" real,
  "geo_id" real,
  "ansi_code" real
);
SELECT MAX("latitude") FROM "c" WHERE "water_sqmi">0.518 AND "longitude"<-99.830606 AND "pop_2010"=18;