The correct answer is option 3: gravitational potential energy. Tides in the sea are primarily caused by the gravitational forces between the Earth, Moon, and Sun. The gravitational pull of these celestial bodies causes the water in the oceans to bulge, creating high tides. As the Earth rotates, the areas with high tides and low tides change.

The energy associated with tides is gravitational potential energy. The gravitational force between the Earth and the Moon acts as a restoring force that results in the rise and fall of the tides. This energy is stored in the form of the elevated water levels during high tide and is then converted back to potential energy during low tide.

Options 1 and 2, hydraulic energy and kinetic energy, are not the primary forms of energy stored in tides. Hydraulic energy refers to the energy of moving water, while kinetic energy refers to the energy of motion.

Alert - correct answer should be option 4: A combination of all the above three forms of energy. Tides in the sea contain a combination of gravitational potential energy, hydraulic energy, and kinetic energy.