If you don't want to use a resource pack, you can use these vanilla methods: Minecraft - Invisible Player Detector (Survival friendly!)
In Minecraft, "Invisible Player Detector" resource packs work by making the emitted by invisible players much larger, brighter, or more distinct . Since a player's model itself has no texture to change while invisible, these packs target the only visual cue left behind by the invisibility effect. Top Resource Pack Options INVISIBLE PLAYERS DETECTOR RESOURCE PACK FOR MC...
: Replaces potion particles with a red "caution" mark and can add a "Steve marker" indicator above players' heads for exact positioning. Non-Pack Detection Methods If you don't want to use a resource