Splashzone is one of the earliest bosses you will encounter in Borderlands 4, but he's not a boss per se. He's a rather large Badass Psycho who's part of the Rippers faction. While not a threat, or rather not deadly enough to send you running for the hills, you should reach level 4 or 5 before attempting to fight him and his entourage.
You will originally have to fight him on the mission Recruitment Drive, so there's no need to rush the process. As long as you have a weapon that deals high DPS, you should be perfectly fine. That said, here's how to deal with Splashzone in Borderlands 4.
How to defeat Splashzone in Borderlands 4

As you enter the encampment, you'll be welcomed by a host of Rippers, and Splashzone will eventually spawn as well. He's not a threat, but it's best to be at a distance while dealing with him. As mentioned, consider him a large Badass Psycho. Here are his attack patterns that you need to be aware of:
- Elemental Trail: Splashzone leaves a nasty trail of ooze as he moves about the map. Stay ahead of or away from him to avoid taking damage.
- Elemental Grenades: Another trick up Splashzone's sleeves are Elemental Grenades. Again, stay ahead of or away from him to avoid taking damage. However, since grenades can be lobbed, take care not to catch a stray fragment since they do AOE damage.
- Running Attack: Much like other Badass Psychos, Splashzone runs about, twirling his weapon as he moves. If you get close enough, you will be hit by it.
- Weapon Throw: When you're out of melee range, Splashzone can get a bit cheeky and toss his weapon at you. Dodge out of the way to avoid getting back, but do keep track of him as you'll need to see when and where he throws the weapon to begin with.
That's about all you need to know about Splashzone. As long as you have a powerful gun that deals high DPS and a solid Vault Hunter build, you should be fine. Remember to stay out of his attack range, and you should be able to tackle the entire fight without taking much damage.
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