Typically 5-15% slower depending on conditions, sighting ability, and whether you wear a wetsuit. Calm lakes with a wetsuit and good drafting can be nearly as fast as pool pace; rough ocean without wetsuit may be 15%+ slower.

Yes, typically 3-7% faster due to improved body position and reduced drag. The benefit is greatest for lean/muscular swimmers with less natural buoyancy. Naturally buoyant swimmers see smaller gains.

Research shows drafting can reduce energy expenditure by 10-20%. Swimming directly behind another swimmer is most efficient, while hip drafting provides about half the benefit.