Re: Unsinkables...
Modern definitely includes 90s and later.
As far as solid construction, you need to see for yourself. Most boats are going to have stringers that the deck is on, and these stringers provide strength. The Whalers, Carolina Skiff, Mckees and such have are injection foam instead of these stringers. The foam is light, but also strong, and reduces hull flex, holds the deck up, and provides ample flotation. It does the purpose of the stringers, and provides flotation and sound deadening to the water below. Now, all boats come with the ability to remain above the surface if swamped, but that is usually due to pour in foam, not the injection molded deal. So, you probably couldn't cut those into four pieces like you can with Mckees and Carolina Skiffs and such.
Your best bet is to go to each manufactures web site, and see what they boast about. Ignore the opinionated stuff, and look for cold hard facts. Most will brag about construction, and by reading the facts on how it is constructed (usually mixed in with sentences of boasting) and by looking at pictures, you can get the best sense of what will work best for your needs and wants.