Can you make Underwater levels where Sackboy can swim or use a submarine?  Also, can make costumes from stratch? For example, can you make pants in the shape you want?  Thanks in advance.

You can make underwater levels, but Sackboy can't swim. You could have a submarine. Regarding the costumes, you can make custom stickers and stamp them onto Sackboy, but you cannot make stand alone outfits.

I've seen one level where they simulated swimming underwater with the use of a jet pack.

Can we turn this into an LBC question thread? =p

What's the penalty for dying in that game? I plan on buying it soon, and after watching a vid of it for some reason I feel like making a map with......lots of explosions =/

on the note of the ports, some ports have more lifes on them so you can get away with dying more. I think the option is 4 or 8. And you can just set up more ports if you think your level is particularly dangerous.