I have done probably 8 flights just this last year with Garuda and they have always been fine.. I don't think the agents even know what most dive gear is. I showed an agent a BP&W set up and she just looked confused so I showed her a mask and snorkel and she was like ohhh ok! I use packing cubes so clothing is not visible but always packed around my dive gear. I usually wrap my bottle of Vodka in my wetsuit as well

I suppose technically just about everything we bring is dive gear "sport equipment" since we don't bring a lot of clothing.