Against what team did the Islanders have a 5-18-5 record?
CREATE TABLE "regular_season" (
  "game" real,
  "december" real,
  "opponent" text,
  "score" text,
  "location_attendance" text,
  "record" text,
  "points" real
);
SELECT "opponent" FROM "regular_season" WHERE "record"='5-18-5';