Ayer, no (nadamos / nadábamos) porque (llovió / llovía) mucho.

Ayer, no nadamos porque llovía mucho.

Translation: Yesterday, we didn't swim because it was raining a lot.

Explanation:

Preterite: nadamos

Imperfect past: llovía

Preterite: with action verbs (swim), it is used when the action occurs (or not) at a specific point in the past (yesterday). Ayer, no nadamos.

Imperfect past: it is used for long-term past processes (rain) and it does not interest to indicate its beginning or its end. The limits of its temporality are not clear and it is usually used to describe a situation in the past (yesterday). Ayer, llovía mucho.

Jugué

Explanation: