I've got the softlock in the 2.0.92 patch sorted out, that'll be going up soon.
Hydro Materia can be found at the docks where the Cargo Ship used to be.
I think it's room-dependent, the back room where Hades is picked up should have that encounter.
You don't miss out on anything unique; status ailments can quickly turn things around for you. A summon like Alexander can inflict Stop while also hitting their Holy weakness, the Shield spell can block incoming elemental damage (negates most of their attacks), things like that.
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Mod updated, 2.0.92
v2.0.92
*) Osmose description updated
*) Temple of the Ancients: leftover debug script was adding Chainsaws to inventory
*) Highwind: Line of dialogue was playing under the wrong circumstances.
*) Sister Ray: Typo on Hojo's line.
*) Midgar Raid: NPC was appearing under incorrect circumstances.
*) Kalm: Depending on where player is when talking to Barret for Catastrophe, a softlock could occur.
*) Corneo's Mansion: If entering on Type B, the Type A events would occur and disrupt game progression.
*) Wutai: Altered some dialogue for Type B on Da Chao.
*) Temple of the Ancients: A button prompt was updated.
*) Satans Gate: Boss respecced, Powersoul drop moved to field script.
*) Red Materia Cave: Adjusted parameters of Zombie Breath, AI script change.
*) Chokhmabo: Unset attack in death script, resulting in softlock.
*) Chokhmabo: Initial Defence stats were not at correct values.
*) Curator: Increased MaxMP of torso to 400.
*) Cobalt XIV: Rearranged order of combatants for an AI trigger from opt to use Laser + Matra Magic.
*) Using other party leaders for Temple of the Ancients on Disc 3 results in softlock on jump.
*) Text Box alignment: Sector 7 slums.
*) Lucrecia Cave: Issue where a different party leader with Cloud/Tifa present would disrupt the script.
*) Documentation: Changed wording of Zenogias Plate placement from Shinra Villa to Costa Villa.
*) Temple of the Ancients: Issue where a special chest could be opened from platform above, causing a softlock.
*) Temple of the Ancients: Issue where Cid couldn't
*) Armored Golem: Updated some attacks for the AI.
*) Da Chao Spirit: HP boost.
*) Ruby Weapon & Emerald Weapon: HP boost.
*) Green Hero: Changed buff given by an ability from Regen to Auto-Crits.
*) Ruby Weapon could be refought after killing him due to a missing flag toggle on his Death Script.
*) Added KO check for Yuffie and Cid's innate abilities.
*) Armored Golem: Some attacks weren't set in AI.
Alexander only hit them for like 1k damage, and they have 20 or 30k hp? And it just never inflict stop, just never. If any or two cast bolt3 or ice3, it's almost 2k damage each, even regular attacks deal close to 1k damage on average, and they are very fast, like fast, and they have counter attacks, like 2 counter attacks?
This is such a massive difficulty spike, it's not even funny. I thought this should be the next destination alongside Junon underwater section but there's no way I am expected to be able to handle the Zack flashback at this point, unless I'm missing something. I do make use of wall and haste, fully loaded Cloud with the best materia I could muster. Had to spam x-potion to keep up, to no avail. Even trying to get to the last battle was much, much, much, much, much harder than any of the boss battles I had before, including the temple of ancient bosses, partially attributed to Zack fighting alone.
Is this supposed to be an endgame fight? Can I put it off till later in the game and come back to it once I got KOTR and the likes?