Unwanted water in cab
 

Passenger side front floor board saturated in water. First thought was leaking door seal but there is no evidence of water from the top of the cab. After talking with my dad (who's in TX I'm in AR) he has pointed me to a leaking heater core. Any other thoughts? This issue is in a 2005 chevy sliverado.

Could be a leaking heater core if you are losing coolant, and you would smell it.
or the drain for the AC evaporator could be plugged up

Thnx, I'll check out the AC plug but if I haven't used the AC would it plug up. I haven't paid attention but the water may show itself after I use the heater.

leak
 

Could also be a leaking under the cowl panel there is alot of welds there that have sealer over them sometimes they leak if not sealed completely.

When you have defrost on the AC compressor runs.
and the auto climate control it turns on above 35 or 40* to keep windows from fogging up.
to check for the cowl leak you could have someone hose it down and look for water pouring in.

Cowl panel? Where is this located?

cowling is the area right under the windshield and is also the area that the AC pulls in outside air....also racerx55 has a good point about the defrost especailly if you don't smell any anti-freeze in the cabin...

How hard is to take the cowling panel off?

I can't speak personally to your vehicle but in general it should not be too hard, remove the wiper arms and remove and screws holding the cowling down, check for leaves, and other debris that might be blocking any drain holes....

thou it might be easier to remove the housing in the cab first to see what you can see