Hydro Hypostasis, strategies, weak points, and achievements

"He" is the Hydro Hypostasis below Watatsumi Island; a being made entirely out of Hydro, giving it an immunity to the element; defeating it will reward you with Dew of Repudiation and Hydro Crystals.

Cave entrances marked on map

Hydro Hypostasis Arena

Strategy

Many Hydro Hypostasis attacks require you to stay on the move, so keep an eye on your Stamina Bar.

Most of the Boss's attacks will leave it open to your attacks and some others during the attack itself, so choose the moments that are more accessible for you to attack.

One of the Hydro Hypostasis attacks summons Water Droplets, an exploding one (dark blue) and a healing one (light blue); they are weak to Cryo and especially to Dendro, both go down with one Dendro hit or two Cryo hits in the case of the exploding one.

At the end of the fight, the Boss will summon three healing Water Droplets; their weaknesses are the same, and destroying them all will end the fight.

Weak Point

The Hydro Hypostasis does not have a weak spot or weakness; aside from its Hydro Immunity, it is equally vulnerable to the rest of Physical/Elemental damage, technically, since its core is always affected by Hydro, Elemental reactions will be really easy to trigger.

You can stun the Hydro Hypostasis if you manage to destroy the Exploding Water Droplet near it.

Achievements

Dry Clean

Defeat the Hydro Hypostasis without destroying a single one of its Water Droplets (except when it is restoring HP.)

Do not attack the Water Droplets when the Hypostasis summons them, only the ones that appear when the last phase starts; there is no problem if you let the dark blue droplet explode by itself.

Bio-Oceanic Weapon

Be hit by a certain animal created by the Hydro Hypostasis...

The animal is a Dolphin; the original name of the Achievement in Chinese roughly translates to "Marine Biologist, Ora!" a reference to Jotaro Kujo from Jojo's Bizarre Adventure.

Salt for My Foes, and Water for Me

Obtain at least three healing orbs fired from the "water droplets" during the Hydro Hypostasis fight.

Wait in front of the Healing Water Droplet and absorb the healing orb it releases three times; the achievement will appear when you get the third.

The Fraught Return

Stop the Hydro Hypostasis from reviving itself without destroying any of the "water droplets" by placing obstacles or repelling them.

The most effective way is to use the Geo Traveler, if you have them at Constellation level 6 better, as it will increase their skill durations; use the Elemental Burst to block the path of at least one or two of them, then the Elemental Skill to block the rest, you'll get the achievement after a couple of seconds.

Water, Basically

Defeat a Hydro Hypostasis in Co-Op Mode.