Don't Jump into the water to help the person without telling someone else and giving the person in the water a flotation device.
My legs cramped I can't swim!
Grab hold!
I'm coming to help!
People who are actively drowning and panicking will attempt to hold onto anything that could get them some air including the person helping them pushing them under.
AHHHH!
Hold on your pushing me under!
Jumping in right away without any precautionary measures can be life threatening for both the person drowning and the person helping.
Ask for help and call 911 in case it is needed and give the person in the water a flotation device to use to get above the water.
My legs cramped I can't swim!
Someone come help!
Once they have a hold on the flotation device pull them towards the edge of the pool and out of the water.
Calm them down and check if they need any medical attention.