Anchor

Oft I must strive with wind and wave,
Battle them both when under the sea
I feel out the bottom, a foreign land.
In lying still I am strong in the strife;
If I fail in that they are stronger than I
And, wrenching me loose, soon put me to rout.
They wish to capture what I must keep.
I can master them both if my grip holds out,
If the rocks bring succor and lend support,
Strength in the struggle. Ask me my name!