Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_13 (s_motor_ship___s_naval_trawler VARCHAR, grand_total VARCHAR)

### Question ###
How many ships for the nation with grand total of 20?

### Accurate SQL ###

SELECT s_motor_ship___s_naval_trawler FROM table_name_13 WHERE grand_total = 20