Well below the surface you could have bumpers with shock absorbers and dampeners.
I made a diagram below.
The islands would be like giant aquatic bumper cars that you can live and farm on. As long as the bumpers are underwater and the portion underwater is wider than the portion over water, it will seem to landlubber eyes as the islands never actually collide.
Depending on the (in)efficiency of the bumpers, some seismic activity might result when islands come close to each other.
As an alternative, you may add horizontal rods to each bumper to make sure that they don't have a full collision, but rather literally push each other apart.