Question 1 with 1 blankayer mi hermana y yo (ir) a la playa. question 2 with 2 blankscuando llegamos, (ser) un día despejado con mucho sol, y nosotras (estar) muy contentas. question 3 with 1 blanka las doce (comer) unos sándwiches de almuerzo. question 4 with 1 blanklos sándwiches (ser) de jamón y queso. question 5 with 2 blanksluego (descansar) y entonces (nadar) en el mar. question 6 with 3 blanksmientras (nadar), (ver) a las personas que (practicar) el esquí acuático. question 7 with 2 blanks (parecer) muy divertido, así que (decidir) probarlo. question 8 with 2 blanksmi hermana (ir) primero, mientras yo la (mirar). question 9 with 1 blankluego (ser) mi turno. question 10 with 1 blanklas dos (divertirse) mucho esa tarde.

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.   

they need to keep water moving over their gills so they seem to have active periods and restful periods instead of undergoing deep  sleep.  they sleep swim

explanation: