I've run into a block and curious if I'm missing something. It seems that I need the red (mechanical prototype) science pack to get to water filtration 2. I need plastic for red science, but I can't make plastic without researching water filtration 2. I think that I spent my starting plastic on belts and inserters and I might be stuck.

Am I missing some pathway to plastic besides the seawater -> saline water -> electrolysis path for the chlorine?

You don't need water filtration 2. Water filtration 2 just enables you to build your own hydro plants and seawater intakes. But you start the game with 3 hydro plants and 2 seawater intakes, which is sufficient to produce plastic. If you're already using all 3 hydro plants for something else, you may need to deconstruct one and use it for something else. If you destroyed your hydro plants you could be in trouble.

Ha, thanks for the quick response! I thought I’d be missing something, completely forgot I’d put down all three for atmospheric science, not that I could supply enough air for all three.

I’ve noticed that energy storage is done through surge electrolysis and combustion of water, probably pure water to avoid the sodium hydroxide, which is a fun touch and something that always bugged me about power in sea block. I’ve automated the first three science packs (but slowly!), gotten my first graphite and filters up so that I can start to scale my chemistry and plastic production. It’s interesting that this mod feels like it wants me to go big on chemistry for plastic early on, it feels like a decent mix of plastic is necessary to scale the infrastructure. I’ll be curious to see where everything goes and also to see just what power infrastructure I’ll need to avoid brownouts. Lots of small power poles for all the turbines!

Good progress for one day! Fully automating the third science pack is a big step.