Shooting zombies in the water when they are frozen

[jdl14]

is there certain zombies that explode when you shoot them in the water?

I've been noticing that when I get a group of them rounded up by the spawn and begin shooting them that they start to freeze and then explode causing a chain reaction killing a whole bunch of them and sometimes hurting george.

Like one explodes causing the others to freeze.. george roars.. and then they all die?

Also has anyone noticed that when you throw a grenade into the water you sometimes get points before it even explodes? Like as soon as it touches the water? Why is that?

Using the chain reaction i've made it to round 21 solo with just using the mp5k and an hk21 unPaP,

[nhcre8tv1]

If you shoot a zombie enough in the water they freeze. Once they are frozen, you attack them again and can kill other zombies around them and startle George. It's handy but can be a nuisance, but I have yet to encounter something that makes it annoying.

[Zombie_Bunneh]

I know grenades give you points when you hit zombies with them, as for the rest of your experience, I have no idea...