Held translucent blocks make the water, clouds, particles, and placed translucent blocks behind them invisible in third person mode.

This is not a duplicate, the held item isn't behind the other transparent blocks, this bug makes the things mentioned in the title invisible!

The transparency effect of the item in MC-186078 overrides the transparency of the cyan stained glass - in your ticket, the item overrides the transparency of the water, hence they are the same issue, or similar enough to not require separate tickets.

The item isn't dropped in this report, and it's not behind the blocks either, but in front, and it's not like the rendering makes it so that there's the rendering of the block and the item together but badly layered like in MC-186078

Instead, the only transparency showed is the one of the item and the thing behind it is completely invisible.

And it's not just water the one that becomes invisible, but also clouds, particles, and placed translucent blocks.

I think this report is reporting completely different things based on these points.