shell A2

/ʃel/ a very light narrow racing boat

skill A1

/skɪl/ ability to produce solutions in some problem domain

shield B2

/ˈʃiːld/ Anything that protects or defends; defense; shelter; protection.

shelf A1

/ʃɛlf/ A flat, rigid structure, fixed at right angles to a wall or forming a part of a cabinet, desk, etc., and used to display, store, or support objects.

shoal C2

/ʃəʊl/ Shallow.