When you step into a very full bath or hot tub, sometimes the water overflows. But when you step into a lake and swim, you don't notice the level of the water rise at all. Explain why this is.

This all simply due to the size of the two water bodies question and the your body size in a bath tub the water is small enough to allow the upthrust displace water out if the tub whereas in a lake the water is bigger and your body size is smaller to allow any noticeable upthrust that would cause an overflow