English Idioms that start with the letter S

Someone who dreams of being famous has stars in their eyes.

If people try to stem the tide, they are
trying to stop something unpleasant
from getting worse, usually when they
don't succeed

People use this idiom to imply that people who are quiet and don't try to attract attention are often more interesting than people who do try to get attention

If you swim with the tide, you do the same
as people around you and accept the general consensus

If something is sure-fire, it is certain
to succeed (Surefire is also used)

Someone who's exceedingly strong physically
is said to be strong as an ox