Here are some six-letter words beginning with "S" and containing "I," "M," and "P":

1. Simple

2. Impose

3. Impair

4. Impala

5. Simper

6. Impede

7. Impawn

8. Impala

9. Impish

10. Imping

11. Impone

12. Impart

13. Impede

14. Impose

15. Impawn

16. Impecc

17. Impels

18. Impend

19. Impiety

20. Imping

21. Impose

22. Impledge

23. Implant

24. Implied

25. Implode