St. Augustine 'Palmetto' Failing in Deep Shade: Conflicting Water Advice

A Miami homeowner installed shade-tolerant St. Augustine 'Palmetto' under a large oak. It's dying. One expert said water 3x/week; another said stop watering. Photos show patchy green, dark patches, a blue tarp (pool?).

The responding expert notes something green remains (maybe grass or wild Bermuda). Asks: installation method (sod/plugs)? Sprinkler system? Dark patches? Blue tarp (chlorine hurts grass)? Conflicting advice may have been right for different conditions—need to diagnose drainage, sprinkler output, and actual grass type.