CREATE TABLE table_name_90 (silver INTEGER, gold VARCHAR(255), sport VARCHAR(255), bronze VARCHAR(255), total VARCHAR(255))
What is the smallest number of silvers associated with bronzes under 20, totals of 1, golds of 0, and in Water Polo?
    
SQL: SELECT MIN(silver) FROM table_name_90 WHERE bronze < 20 AND total = 1 AND sport = "water polo" AND gold < 0