in lost tower . it is on route 209. when you see the 2 ladies at the top talk to them. i /think/ you might have to battle them. i doubt it though.
With hm strenght.
The HM dive cannot be acquired in Pokemon diamond.
Strenght is an HM move, teach it to one of your'e pokemon. to use it just select your'e pokemon and select strenght.
whirlpool is not classified as a HM in that Pokemon series, only in heartgold/soulsilver is it a HM, in diamond it is only a simple TM (1use)
first of all there like ten Hm
Fly, Surf, Strenght, Waterfall, Cut, Dive.
Go to Iron Island and talk to Riley, he'll give it to you.
The HM strength
Bibarel + SkuntankorBibarel + Drifblimthere is no hm slave
in Nimbasa city the building on the top left talk to the lady on the left
There is no HM called dive in Pokemon Diamond you fat oaf.
Celestic Town