So i started a new game of Sea Block and suddenly i can't build my first lab since i need tin now for the belts.

I had the same problem, I went digging in the mod files, specifically "...AppData\Roaming\Factorio\mods\SeaBlock_0.2.4" open the prototype folder then technology.lua in notepad++ or your favorite editor, then search for "transport-belt" there should only be one occurrence, then all you have to do is add basic in front of transport belt "basic-transport-belt", save the changes and exit out of the folder tree, that moves the basic transport belt recipe to the basic circuit board research, it does mess with the naming of the basic transport belt, but it least it makes it playable.

Unfortunately that didn't work. My guess is that maybe any of the Bobs had an update but don't know which one.

You can always alter the tech tree in the SeaBlock so that Basic Circuit Boards unlock the Basic Transport Belt. The Lab that needs crafting for me requires 4 of the basic belts and I had a problem that I needed to craft the lab to unlock the belts needed to craft it.

{type = "unlock-recipe", recipe = "black-transport-belt"},

@Almighty_Cumpet, do you need to go into a specific file for that command you posted?
I figured it was something wrong when I couldn't make my first Lab as well.

@Khaylain, yes you will need to extract the mod from the zip file and go into the prototypes folder to edit the "technology.lua" file. You can open the file in notepad or any text editor, I would recommend notepad++ at least though as it will make viewing the file much easier. This is only a temporary fix of course and I'm sure the mod author will either include it as an update or change it to be different.

By extracting the [SeaBlock_0.2.4.zip] archive, going into [prototypes] folder and finding the [technology.lua], and adding the line [{type = "unlock-recipe", recipe = "black-transport-belt"},] to the first instance of [type = "technology] under [effects = {] I got it to work.

Thanks to Almighty_Crumpet for the info.

@Khaylain, looking at the change log for the most recent update it seems the mod author has added in the unlocking of basic belts fix so it should work without editing the files now :)

This is because bobs logistics adds the black-transport-belt, as a first belt, to use when there isn't any tin yet in your bob's mods factory. Problem comes when you add SeaBlock, in which tin is early midgame/late early game.

For me, transport require steel plates, which isn't an improvement either, but and I am trying to find out which mod changed tin to steel... no luck yet