Welcome to Pond Boss, IowaNate, as others have said.

I have been surprised by how much weight it takes to sink down and hold down pallets when they are first placed in the water.

Does your sketch have two or four cinderblocks?

I even wonder if four cinderblocks would hold down that many pallets right away.

What I've tried to do is also use and anchor & rope type of extra cinderblock to minimize drift if the cluster does not sink right away; the lead between the anchor and cluster has to be long enough to compensate for varying water levels if that happens in your pond.

Structure is a labor of love.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."