First crack at CS4 auto-blend, need some help

I'm having a bit of a transparency problem on this. As you can see, the horizon shows through the person's midsection. This is my first attempt at photo stacking so I'm not very familiar with what cam be done to correct it. I'm using Photoshop CS4 (auto-blend).

If anyone could tell me what causes this or how to fix it I would greatly appreciate it.

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The Auto Blend Layers is more to create an HDR than it is to creat a composite like this, although it uses a similar approach. I'd suggest the Auto Align Layers as a better starting point.

With each image in a layer on top of each other select all layers, then do Edit/Auto Align Layers. Mask each layer above the background layer (add layer mask and fill with black -- click on the layer mask and click Ctl->Backspace). Then you can brush in each boy out of his own layer. If the exposures are the same, you can be pretty broad with your brush. If the exposures are not the same, you will only be able to brush the boy in, so use whatever tool you know to get the right job -- you'll need to be 100% opaque for each boy to avoid the transparency not only on the boy with the horizon but with the lowest one down (waves in his midsection).

Thanks, I tried something similar but did not fill in with black. maybe that was my problem. I'll give it another try.
EDIT:
No luck. Auto align only showed 1 frame even with all the layers selected. It's not until I select all layers and do edit/auto blend, that all frames show up as one picture.
below is another one I did. Same concept, different person and set of photos. Using the same method as the first one, I got these results.....Much better with this one, just not sure why.

OK, if you mask all masks black, only the bottom layer shows up untilyou "reveal" something from an upper layer by painting white into the mask.

Try starting this way to simplify things: after all upper layers have a black-filled mask, first turn off visibility of all but the background and lower layer so you won't get confused, then click on the mask of the layer on top of the background (the only other visible one). A little white rectangle should surround the black mask. Now, look over at your color picker toward the bottom of the toolbar -- it should show black as the foreground color and white as the background -- if not, click "D" to set the default colors and it will be done.

You will see that the image appearing is the bottom blackground layer.

Now, click "X" to switch the background and foreground colors -- you will see the foreground white, the background black.

Now, click the Eye icon for the active layer on and off to ensure where the kid is, then select the Brush tool ("B") and paint white over that area and you should see the kid appear (you will see a little white appear on the black mask, Even though you are painting a boy into the image).

That's some beginning ideas. Check out this thread, I think you'll find some very similar aproaches:

https://photography-on-the.net/forum/showthre​ad.php?t=684724