The pronunciation of “agual” in Spanish varies relying on the area, however the commonest means is “ah-gwahl”. You will need to word that the “u” is pronounced as in “true”, not as in “glue”.
In some elements of Spain, “agual” is pronounced with a silent “h”, so it appears like “ah-gwah”. In different elements of Spain, the “a” is pronounced as in “father”, so it appears like “ah-gwahl”.