Where is HM Rock Smash on Pokemon Fire Red?

You need a Pokemon with surf. Go to the right until you reach Kindle Road. Swim upwards and keep going until you see a cave, which is Ember Spa, on your right. Walk in and go to the right and then up. You'll see a bunch of people and springs. Then you see an old man in a blue shirt at the end standing near a waterfall. Talk to him and he gives it to you. Hope this helps!