Why is water going straight to oil pan in my 1997 Toyota Tacoma 2.4

By far the most common cause for what you're seeing is a blown head gasket. There are multiple oil and water passages between the engine block and the cylinder head, and once the head gasket fails, it allows water into the oil passages, oil in the water passages, or both.

Are you seeing other symptoms like white or black smoke out the tailpipe? Have you used a block check kit to see if there are hydrocarbons in the cooling system? Is the water similarly contaminated with oil?