Looks like Rob has been busy. 
The Air Tractor aircraft are available, the cropduster you have seen, and this is the firefighting unit with floats.
Important: Initially the engines are stopped, use the B key to start or stop engines. The aircraft when first placed has the wheels down for land operation, invisible track on land or water should be at ground level, zero. Water level is 3 metres lower, -3 metres. In Driver, press the H key and the wheels will retract and the aircraft will lower to the water level.
More information on my webpage:
http://ianztrainz.com/2012/03/air-tractor-at802f-firefighter/
Ian

The Air Tractor aircraft are available, the cropduster you have seen, and this is the firefighting unit with floats.

Important: Initially the engines are stopped, use the B key to start or stop engines. The aircraft when first placed has the wheels down for land operation, invisible track on land or water should be at ground level, zero. Water level is 3 metres lower, -3 metres. In Driver, press the H key and the wheels will retract and the aircraft will lower to the water level.
More information on my webpage:
http://ianztrainz.com/2012/03/air-tractor-at802f-firefighter/
Ian