Not that I actually have any care for making boats, but satisfactory buoyancy would be simple enough - apply thrust equal to one (insert ship size) cube of water upwards to each cube under water level.
On the plus side, they seem to have done some nice updating to the Oxygen system, as air now seems to flow around most partial (thin) blocks. There are still a few blocks that need some attention though, especially some of the new(er) ones, such as the Square Block with Round Hole and Square Block with Square Hole - these are both "airtight", yet air should flow through the holes - especially since we can walk through them.
The old Oxygen system determined pressurization on a case of whether a block's space was airtight or not. Only allowing true or false options for the entire block space. The new one breaks a block's space into a set of 2x2x2 cubes and each one of those are now used in the same way as the old method, only allowing more fine control. Those hollow blocks can't be made to allow air through them since they're hollow in the middle but solid around the edges; and a solid wall on 4 sides is more use airtight than one that's not airtight on any side.
