When sourcing an amphibious ATV, the most critical factor is the hull design and material. Look for High-Density Polyethylene (HDPE) integrated bodies which offer superior buoyancy and impact resistance. Ensure the engine is a marine-grade or specialized off-road engine (e.g., Kohler or Kawasaki) with a high-output cooling system to prevent overheating during land use. For aquatic performance, verify the water speed (typically 3-5 mph via tire displacement or higher with an outboard motor) and the maximum payload capacity for both land and water, as water capacity is usually significantly lower.