When evaluating fiberglass pools, the structural integrity and gel coat quality are paramount. Ensure the pool shells feature a high-performance gel coat that is UV-resistant and chemical-resistant to prevent osmosis and fading. The laminate layers should include vinyl ester resin, which acts as a superior moisture barrier compared to standard polyester resin. Additionally, verify the wall thickness consistency and the presence of reinforced ribbing or 'closed-beam' construction to ensure the shell can withstand hydrostatic pressure once installed.