First and foremost, the amount of effort you put into visualising this suggestion into reality is absolutely insane, so props to you. Next up, my personal thoughts about each aspect of this boss.
Attacks -
I don't really like how you made it so that it isn't land friendly. Just by looking at the general size of the boss it surely should take up about 2/3 of the ocean area, if not more or less. Some certain attacks (jump attack, mine attack in water and the front cannon guns attack are a few that come into mind) should be nerfed so that they happen less often, if not prepared this boss should destroy you in seconds with those certain attacks.
Drops -
Does the Shellshock mask have a functional aspect to it or is it completely a vanity item? Oh, and what are the contents of the treasure bag that comes with beating this boss on Expert Mode. Few things you could've clarified in the suggestion.
Crafting -
Why Gold and Iron Bars of all things? Gold and Iron Bars aren't exactly found in all worlds, maybe make it so that the equivalent of Gold and Iron bars (I think Silver or Lead, but I might be wrong) can be used in crafting these items too?
Armor Set -
Not exactly the best armor set in my opinion (debuff that comes with using the helmet as part of the armor set set doesn't make it any better either), there are better armor sets that can be made after beating the Mechanical Bosses (Turtle Armor and Chlorophyte Armor are a few examples of what I mean)
