A countdown on their face indicates when they'll explode, but Mario can spray them to turn them blue and momentarily harmless, then throw them at enemies.
Bob-ombīob-ombs have an odd appearance in Super Mario Sunshine - they appear to be more mechanical bombs than in other Mario games. They cannot be defeated except by a Yoshi eating them, but they are useful for Mario as he can bounce on their heads to reach great heights.
Pondskaters, Skeeters, or Blue Spiders return from Super Mario 64 in Super Mario Sunshine.