[Hydroid]'s base kit is entirely focused around abusing abilities while in Undertow. This build attempts to utilize all of them without subsuming another ability. Stats and survivability are kept as balanced as we get them with the mod slots available.

[Corrosive Projection] is needed because Corroding Barrage no longer completely strips armor after the corrosive nerf. Undertow has trouble killing through armor. Replace it if you're going against unarmored enemies.

[Rolling Guard] protects you in between Undertow casts. You'll eventually run out of energy so the invincibility gives you time to grab energy orbs to proc Energize.

Corroding Barrage can be replaced with any other augment if you're going against unarmored enemies or you have another way to strip armor.

Arcane Aegis gives you additional time to roam outside of Undertow if it procs during [Rolling Guard]. If you don't like the RNG aspect of it you can replace it with any other arcane to suit your playstyle.