Bubbles in Fiberglass in-ground pool

So with this heat we have had here in Sunny CA, it seems like there are more and more of these maybe 2" around little bubble like things on the bottom of the shallow end (3.5'-4.5') of the pool. Last year there were a few, 6 maybe, now I'm up to 20+ of them. You cannot press them down, so they do not seem to be flexible.
What are they? What causes Them? What should I do about them?
Thanks, Scott<-
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In typed:

Sounds like delamination; incorrect install or bad material. Check your warranty and make some calls.
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I believe it was installed in 1991? We are new to the house/pool (10/2003), so I'm not sure who installed it, etc.
How long to Fiberglass inserts last? is 15 years a long life for these, or Short or?
Thanks, Scott<-
typed:

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I'm wondering why new ones are sprouting and why only in the shallow end. Might you or your kids be damaging the bottom with a hard object. Maybe jumping in with a toy. The shallow end is far more succeptable since it is easier to contact.
Was the pool drained leaving the shallow end exposed to the sun or chemicals. I'm sure you've not seen a freeze.
If it is a standard Vinyl pool liner than maybe you have some pinhole leaks and what you see is a blister of water between the liner and pool wall/floor material, perhaps between two layer liner. If that is the case, the liner needs to be replaced. What is the pool made of?
best bet is to pay for pool service at least once so you can learn what you are missing.
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I don't think its kids toys. Could be the Kids. The only ones really in it of that age are my 2 nephews, one cant touch the bottom and the other is 6, so he might, but I don't think he could make that hard of an impact on the bottom.
Pool was never drained. Never Frozen. Though it has been the hottest we have ever seen it. In the mid/low 90's No Heater, just with the cover and the sun. This has been the hottest since we've lived there. (Northern Calif)
Its not the gunnite (sp?) type, I think its a Fiberglass insert.
I did have a pool guy out once, he was pissy they we didn;t retain his services after we bought the place. I told him I didn't know he was the one who maintained it. Anyway it checked out fine. He showed me how to clean the filter, etc and the Chemical part I knew about. The bubble were not there at the time.
Thanks, Scott<-

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Scott Townsend writes:

If they're bubbles in the pool wall, drain the pool, grind them down, fill with epoxy, and polish smooth and flat.
If it is a lime deposit, chip it off.
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Can you do that with fiberglass? How do you color match? With 20+ of these I'd not want it to look like the pool has a bad case of acne...
Thank you, Scott<-

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Scott Townsend writes:

Yes. What you call "fiberglass" is actually glass fibers in an epoxy matrix.

Try a boat store like West Marine or Boater's World. Tons of stuff to repair fiberglass. Your "pool" is actually a boat, inside out and stuck in the ground.
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