I'm not a scientist but Mythbusters proved that water stops bullets almost instantly so I bought that water that deep could stop a lot of the explosion but I would imagine the splash should have been bigger than that. I guess they had to show that the radioactivity didn't get airborne. I still like this show a lot. They throw enough "things are not what they seem" moments into it to keep me intrigued. It does suffer a bit from what I call Criminal Minditis. That is that the plot and/or killer is complex enough that by the time they've set everything up it's like "oh, two minutes left, there he is, we caught him, the end". Both shows could benefit from some two-hour episodes.