This is really just a nitpick.

Researching Aquatic logistics gives you all of the recipes for all of the stack inserters and belts that you could ever have. However, at the time that you research it (green science) most of the prerequisite things you need to craft them (namely, their inserter/belt counterparts like the bulk inserter, stack inserter, turbo belt, etc.) are obviously not available yet.

I think it'd be a little more slick if there was an "aquatic logistics" tech that came after the prerequisite crafting materials have been unlocked, that unlocked their floating counterparts. Or at the very least, hide the items in the crafting menu until you have what you need to build those items. Not sure if either of those solutions are viable though. If it's too much effort, fair enough :)

I wanted to do such a thing, but it seemed both complicated and clunky to make a subtech for flotation of each inserter/belt tier, and I haven't yet found a way to hide the floating recipes until their base counterparts are researched.

Totally fair - consider this just a standing feature request that you can tackle at your leisure

I second this request. Although as a mod author who has regularly had to do technology-copies for their mods, it is definitely an annoying thing to implement.

Simplest way might be to just copy the unlocks into the same technology as the base inserter, with some exceptions that are either enabled at start (like burner inserter) or come before the Aquatic Logistics tech (like long and fast).

Though there's probably no easy way to prevent someone from unlocking an inserter without researching Aquatic Logistics first, which would unlock the floating variant without having access to the platform. I think I would personally prefer the alternative, even with this pitfall, just to keep the crafting menu cleaner for a little while longer lol