Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_90 (silver INTEGER, gold VARCHAR, sport VARCHAR, bronze VARCHAR, total VARCHAR)
### Question:
What is the smallest number of silvers associated with bronzes under 20, totals of 1, golds of 0, and in Water Polo?
### Answer:
SELECT MIN(silver) FROM table_name_90 WHERE bronze < 20 AND total = 1 AND sport = "water polo" AND gold < 0