If you blow it up in photoshop you can see the pixels of the fish are 4 times the size of the background pixels and you can see in the edit on one of the pictures that the guy or gal that did the photoshopping cropped part of the dude's finger off .. I'll show ya what I mean as you can only get that kind of effect from a photoshopping blow up and past on using the lasso
here's the mistakes they made by photoshopping it ... here's where they cropped off part of the finger with the photoshop lasso

here is the original photo I took the top pic from and if you look at his index finger you can see that there is something wrong with the finger or it looks like it's pointed. This is a common error you get from faking a photo.

also on that second pic there appears to be a line on top of the fish's head where it meets the background water ... that's because of the lasso can't follow the line of whatever you're lasso'n perfectly and it creates a stair step effect of the distorted pixels where they meet the unaltered pixels in the background ... I'll show you in this photo as you can see on the bottom where the fish's head is that the pixels are 4x distorted compared to the water pixels on top left which are much finer pixels. and I've outlined the stair stepping effect that's created by the photoshop lasso so that you can see it easier. and that stair stepping is what produced that line on top of the fish's head.

also on other photos like the one where the fin is a lot smaller below the water on the closeup shot because they couldn't alter that and make it look right so they used the fish's original fin and just blew up the head above it ... to where on the other photo where you see the fin above the water and the picture taken from further away the fin is twice as big above the water as it is below the water in the closeup shot. like on this photo where the fin is below the water .. I'll post this pic again so you can pay particular attention to the fin

now look at the fin when it's pasted beside the fin above the water. It's actually a lot smaller where it should have been a lot bigger in the closeup and even bigger than that due to the water's magnifying effect as things under the water appear to be 10% to 20% bigger and this fin is actually a lot smaller because it's not blown up like the one above the water is.

The reason I know this is cause I've worked with photoshop quite a lot in editing photos like this just playing around but I've never lied about a fish like they're doin. I've made a few fake pics that appear to be eating a man and what not but the guy is smiling and posing for a photo ... he wouldn't have been smiling if a fish was about to clamp down on his whole body hahaha. but these photos are totally bogus as you can see when they're blown up.