But I am really far in an ocean-only Minecraft hardcore playthrough. Like 30 days or something. Full diamond armor, enchanting table, multiple bases, doing really well. I need to fish a hell of a lot more to get the leather I need to make books, to in turn make bookshelves, but other than that I am doing quite well. Also contemplating building a mob grinder, though historically that is where my playthroughs take a shit because inevitably a creeper will drop on me and blow up.
Maybe just stick with cooking kelp for XP.