suggestions?

So today was day 1 of potty training DS (he just turned 3) and it was less then great.  I put him in under pants, and his potty is easily accessible to him.  We have yet to have a drop of pee make it to the potty.  I have been going in at 15 min intervals and putting him on the potty, nothing.  After 5 mins, we put our under pants back on and try again...but in less then 10 mins the under pants are wet.  He is not the most verbal child, but being in wet pants does not seem to phase him at all.  He is not calling for me, crying, saying "uh oh" nothing, he just pees in his pants and then goes on with his day.

I have sat in there with him for longer periods of time thinking that maybe he is just nervous to "let go" and nothing, but as soon as he has under pants on, he's peeing in them and it happens so fast I can't even catch him in the act to put him on the potty.

Any suggestions would be greatly appreciated.