Around 20 metres seems to be the magic depth for snapper. Any deeper and snapper, particularly large specimens, become increasingly difficult to release successfully, but catch them in shallower water and releases are usually straight forward.
There are always exceptions: large snapper can be more difficult to release successfully than smaller examples, but the big ones are often the fish we want to release – they are generally poor table fare and their genetic contribution to the fishery is valuable. Sometimes big snapper struggle to swim back down again even when the water is only 15m deep, a combination of an inflated swim bladder and exhaustion after a vigorous struggle on the line.
In that case, rather than risking catching another big fish, which may also be difficult to release, it might be better to either move to even shallower water, or else join the crowds targetting the work-ups in the deep, where you can probably catch a couple of school snapper for the table in quick time.