Answer: These are the correct answers:
1. fuimos
2. era // estábamos
3. comimos
4. eran
5. descansamos // nadamos
6. nadábamos // vimos // practicaban
7. parecía // decidimos
8. fue // miraba
9. fue
10. nos divertimos
Explanation: Just to elaborate a little on the answer, it can be added that in this exercise they are asking you to conjugate the verb with the appropriate tense. Since the sentences refer to actions in the past, you may use the "pretérito imperfecto" (era, nadábamos, estábamos, practicaban, parecía), and the "pretérito perfecto simple" (descansamos, nadamos, comimos, fue). The former refers to an action that took place simultaneously to another action in the past, whereas the latter refers to an action that took place before the time when the speaker is talking.