1/ action interupted by another one
- as I was walking the alhuge wave crached into me
-when the dog went under water I was swiming
2/two action happened in the past and finished
-when the rescu happened we were on holiday in australia
-peopole were on holiday when the shark attached lst summer
3/sumultaneuous actions
-while the surfers were surfing the dog was swiming water
-you were helping the dog while I was taking photos