Wall cracking

You must drain this pool ASAP. It will burst the next time you have a strong rain, wind, anything that causes the water to have a lot of motion. Each gallon of water weighs 8 pounds, and the water is constantly pushing downward and outward with equal force. The physics of water is that it will always seek level, it wants to be spread as far and as thin as it can reach. A 24 foot diameter pool has about 17,100 gallons of water. When that wall fails, and it will fail if it is not drained, all that water is going to crash into whatever is in its way as it seeks level. So whatever that crack is facing is going to take the brunt of all that water being released at once. If it is facing your neighbor's home or garage you will be liable for any damage done to their property and it may not be covered by your homeowner's insurance.

My own pool had a catastrophic failure during Hurricane Harvey. I was fortunate that there was only minor damage to my fence (other than the total loss of my pool). There is a link in my signature documenting my pool's demise, along with pictures of a similar failure of my sister's pool and a video I found online that captured a pool when the wall burst. RIP Rusty Vogue Pool

Once the pool is drained you might be able to repair it with a matching sheet metal piece, but you will need a lot of time, patience, and a new liner. I would only attempt a repair if the rest of the pool wall is rust free inside and out. You may be surprised at how rusty the wall actually is when you see the inside of the pool wall.. Often you are better off buying a new pool.