Sea ice has the strangest effect on waves and swell. The winds pick up, blustery, wild. Normally the sea would rise as well, short wavelength wind waves, choppy with spray, and the larger swell waves, mounding the ocean into heaps.
But when the sea is covered with ice this has a damping effect on the waves.
In the patches of open water you still get wind waves, high frequency and small. The wind blows spray off their crests, but they never grow very big.
And then the swell comes in and the ice heaves and creaks.
But the waves are damped down, and, for the amount of wind blowing, the sea seems strangely quiet, shifting gently beneath its icy cover.