When trying to grow sea grass using bonemeal on sand blocks submerged under water, no sea grass appear, but the bonemeal is used up anyway. With more water source blocks on top, sea grass appears.

To reproduce:

Place sand blocks, and pour water source blocks over to cover. Water should be 1 block deep. Use bonemeal on sand block.

Expected result: Bonemeal is used up, sea grass appears.

Observed result: Bonemeal is used up, no sea grass appears.