Running through a runnel made of barriers covered with lava gives the appearance of runnign through lava when you are in fact running through air, see screenshots (with barriers visibile and invisible for clarity)
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Duplicate of MC-47520
this has been reported multiple times and btw it dose not mater what block it is (including air) if your head is between 0.5 - 1.5 blocks below the water/lava you will get the underwater/in-lava effect but