Damn, that was quick!
While looking forward to this weekend when I'll be able to try it out I just had to do a test on dry land to see how the DCL-20 would do on my PT20. As indicated I have to zoom in a bit to avoid vignetting but I'm nevertheless quite pleased with the angle achieved. My guess is I'm ending up somewhere around 95 degrees under water. Also of note is that the lens is designed to have water between the port and its body, so focus isn't quite right on dry land.
Here's my garden with the standard lens
And here's the garden with the WA, slightly zoomed in to avoid the black shadow of the port.
K