Nice work with the carbs Prutser. I would have made one of the cover plates name "Crosby" - thus having Bing Crosby ... It is not just the depth of water that is the problem for the carbys - but also the length - a short deep crossing is OK.. longer than say 4 meters is a problem. Did this work? Somehow I think as the low point for the gearbox breather is the gearbox you will still have the problem. If you had a 'Tee' piece with the upper 'Tee' being the air breather and the lower 'Tee' being the drain for the water - seal the bottom of this with enough volume for a fair bit of condensation. The final drive is a bit harder to arrange a water trap for... as it mounts pointed down.