Possible Leak In Pool?

[butterflyblue]

I own a home with inground pool in Vegas....pool was probably built around 1970...I presume it's a traditional gunite/plaster type of pool (it's not a vinyl liner, looks all original).

Had the pool inspected as part of the home purchase in 2010. Other than some falling tiles and a bit of "heaved" up area on the surrounding deck caused by a small fir tree (landscaped around the deck), everything seemed to be in okay condition.

Swam in the pool last year, noticed no problems. To my shock upon getting into the pool for the first time this year, I noted several areas in the shallow end where the bottom of the pool in certain spots was squishy or bobbing up. I reached down and pressed with my hand and indeed, these particular areas were very squishy and floaty, almost the way a liner would be. But this is concrete/gunite ...never had an experience like this (owned a pool years ago that was a new pool), so I'm naturally very concerned. So, I'm trying to figure out what the heck is going on with this, if there's a leak that has somehow gotten under the plastic and affected the gunite/concrete beneath. I haven't had a pool company out to look at it yet as I'd like to have some unbiased info here first. I take care of the pool myself, clean it with a typical pool vac.

Question: could the suction of a pool vac have dislodged the contact between plaster and gunite and allowed water to bubble in there and cause this floaty/ squishy phenomenon in these selected areas? So far, I haven't been able to visually detect a crack, so it may be something subtle going on. It really freaked me out, to say the least. Could tree roots (small but enough to have caused some heave in the patio), created this problem? I have somewhat felt I'm having to add more water than usual to keep the water level up, but this is a very hot climate out here so it could be a normal amount.

Should I do a leak test? and if so, what type and how? The only other thing that I did to the pool was to drain the attached spa so I could retile some areas around it so it wouldn't get wet. I left the spa empty for about 7-8 days back in May and refilled it. I wouldn't think that would have made a big difference to anything. To make clear, the pool isn't "floating" or some such thing. It's these isolated areas on the bottom of the shallow end. I have no idea if there's anything going on in the deep end, I can't dive down to investigate the pool floor down there. Thanks so much for any info or advice!