What is the role of the sea in "Riders to the Sea"?

In Synge's "Riders to the Sea," the sea is that which
provides a living, such as it is, for the characters of the small cottage. 
Unfortunately, it is also that which causes their
suffering. 

The men of the family, past and present, were
and are trapped, in a sense.  To make a living, they must go to sea.  But the sea is the
bringer of suffering and tragedy.  They are, in effect, in a no-win situation.  They
must go to sea to survive economically, but death on the sea is so common that all of
Maurya's sons, as well as her husband, are killed on
it.

Set on an island, the play's characters are, of course,
constantly surrounded by the sea.  The sea, therefore, pervades the play, contributing
to the tragic mood.  For Maurya, the only escape is to lose every male in the family. 
She finds a sort of peace when she loses everything she has to lose.  Having nothing
left for the sea to take, Maurya no longer has reason to fear it.  She is a tragic
figure resigned to her suffering.