I lived in the Caribbean for thirty years and made many observations on changes in beach consistencies.

I observed that whenever someone built a pier out into the water, especially but not limited to stone and concrete piers. The beach sand content changed.

When shoreline structures such as piers are built, they alter the effects of ocean waves, currents and sand movement. The construction, presence, and use of small docks and piers in the coastal environment almost always have potential consequences.

Have any structures been built anywhere in the bay water?

We also have to remember that the sea is rising about 3mm a year worldwide. So, each day, week, month, and year a little more sand is picked up at high tide and during storms and returned to the sea.