Table: submarine_incidents
Columns: date
name_of_ship
nationality
tonnage
fate

Question: What was the average tonnage for the Siljan ship from Sweden?
SQL: SELECT AVG("tonnage") FROM submarine_incidents WHERE "nationality" = 'sweden' AND "name_of_ship" = 'siljan'

Question: What was the average tonnage for Beatus, raided on 18 October 1940?
SQL: SELECT AVG("tonnage") FROM submarine_incidents WHERE "date" = '18 october 1940' AND "name_of_ship" = 'beatus'

Question: Which ship was raided on 26 September 1940?
SQL: SELECT "name_of_ship" FROM submarine_incidents WHERE "date" = '26 september 1940'