Sealed cylinders filled with material that does not sink (plastic bottles?). These tubes lashed together to support a deck. Onto the deck modules can be attached: cabins, kitchen, workshop, lavatory, storage, navigationmodule. Designed and built by different persons.
Three masts like a squarerigger (or old viking ship). Oars and maybe a propellersystem linked to bikes.
Three smaller dingies can be made unsinkable and be liferafts aswell.
Not too much electronics: GPS, compass, charts, IDtransponder. Solarcells.
A tribute to low tech.
Does not have to be decided yet - it will be where ever the winds brings the raft (which will undoubtly be a bad tacker). But tradewinds from europe will probably take the raft to the caribbean or southamerica (if some calms can be endured). If it is still deemed seaworthy next step could be through the Panama canal to the pacific or to South Africa and on to the Indian ocean.
Whalewatching from a platfrom in the mast - followed by:
Freediving with seamamals. And also some deep freediving experiments out in calms in the Sargassosea.
Plastic cayaks, mountainbikes, spearfishing, underwater photo and filming, equipment for rockclimbing.