Because there is water everywhere by which the water gets hot and vaporised so that's why near the sea temperature is low.
The unit for work J can also be written as Nm. Therefore, it is a derived unit as different SI units are needed to obtain its value. In this case, its derived from force and distance.
(Mass does not affect the pendulum's swing. The longer the length of string, the farther the pendulum falls; and therefore, the longer the period, or back and forth swing of the pendulum. The greater the amplitude, or angle, the farther the pendulum falls; and therefore, the longer the period.)