Web Resource: If you need something a little more than even a Land Rover..

Aton Impulse makes Advanced All Terrain Amphibious Vehicles.  Check out the link goes thru to their company website on a page with a demonstration video.

Marketed for snow and water rescue, commercial exploration, and other uses, this would be the vehicle to get if a Land Rover did not get you everywhere you wanted to go, me thinks.  

That or just go for a helicopter?... tank??..

 From the company's website, more info:

- Breaking new ground in amphibious off-road vehicles

- VIKING represents years of research and development work to create a vehicle for the stable niche of corporate, government and recreational off-road and amphibious use.

- Extensive joint testing of prototypes with our early corporate customers has ensured that our vehicle remains true to its mission

- every design feature and innovation is based on improved utility rather than innovation for its own sake. - Unique product ideal for a wide range of specific customers including exploration, mining, maintenance, border patrol and rescue services.

-- VIKING combines Vehicle Type Approval, allowing it to operate on road as a standard car, with off-road ability comparable to tracked vehicles and world-leading amphibious capabilities.

-- Off-road, overwhelmingly superior to comparable amphibious vehicles in terms of comfort, cross-country ability, maneuverability, turn-over resistance and endurance.

-- Safety and comfort when driving off-road, particularly in remote or hazardous areas, regardless of natural, climatic and weather conditions.

-- Unrestricted ON-ROAD USE through a Vehicle Type Approval Certificate.

-- High-floatation boat frame for full amphibious operation.

-- Water propulsion system which can drive the vehicle at speeds up to 15 km/h, allowing safe crossing of in-land water obstacles even against the current.

-- Comfortable, spacious 7 seat cab with attractively styled modern exterior.

-- Outstanding maneuverability - turning radius of 8.6 meters.

-- Remarkable roll-over resistance due to a low center of gravity.

-- Independent pneumatic front and rear wheels suspension with adjustable clearance and powerful tire air-pressure adjustment system operable from the cab while driving the vehicle.

-- Low ground pressure balloon tires minimize environmental impact and soil damage.