Severe oil leak between the engine and the gear box

Gear oil is thicker and smells different than motor oil. If you have to continuously add motor oil to the engine, then it's likely the rear crankshaft seal is leaking. Check the rocker covers too.

what gear box.
5speed manual "GL4 gear lube 4, can stink bad"
or autotmatic. (ATF pink fluid, and smells sweet)

what engine, some engines, leak oil and goes to the bell housing
then down hill (gravity and wind) to the exh. pipes.
what engine, the 2.7L V6? or G16 or J20? what?
and on calif cars they have calif exhuast, and fits up different,..
so no country stated, or if in calif. (exhaust questions....)

if the gear box leaks, (any)
we first check to see if its overfilled (Jiphphyboobs/syndrome)
if M/t the side plug inspection port, and transfer case.
if A/T box. (automatic) we read the operators guide, not guessing how and read that on a hot running engine we check ATF levels.
if overfilled the ATF foams and will leak and cause bearing failure.
air bubbles do not work right as lubrication... ever.
filled to hot mark on dip stick
unless the stick is missing, as is true on newer cars.

if trans leaks, say where it leaks.
top , bottom
front or rear.??

pretend we are blind. and win.

oil in the bell housing can be rear main seal and it can also be input shaft seal in the gear box if manual. The sump bolts on the rear main cap and will leak next to the bell housing indicating a main seal . If auto then the seal on the converter will leak and the oil will leak out of the bell housing. If you are convinced that it is a main seal then check that there is no crankcase pressure issues to make it leak. Change the engine oil and clean the area and if the oils is clean then that will indicate engine or gear box. Put a white chalk line across any oil paths and watch for it to cross the chalk and change the chalk colour.

If it is the front seal in the gear box then the box has to come out. The seal is in the extension housing that the clutch throw out bearing runs on and the seal can be replaced by removing that housing . However mostly if that seal leaks then the front bearing on the clutch shaft may be failing allowing the shaft to move and that is why the seal leaks. If the front of the box is dry then the oil leak may be the rear main seal of the engine so it is best to check both arrears as the oil leaks from the same point in the bell housing

Check the sump gasket at the rear of the sump tension sump bolts. Check that the rocker cover gasket is not leaking down the back of the engine and giving the appearance of a sump leak. Rear crank seal would be another point of leak and front input shaft (clutch shaft) seal leaking. Check the engine oil level and correct if necessary and check gear box oil level and correct if necessary. If you have an auto the oil will be pinkish and indicates a torque converter to gear box seal leaking.. Either of the shaft seals will require the box removal for repair.

hyundai getz.,, if you r in phil. try to call me.. i fix it., anyway what kind of oil leak cause many kind of oil looks a like..

Looks like you have a leaks problem in your gear box. You'll need a clean hand pump to top up your oil. Make sure your pump is clean. In your gear box, there should be 2 ports ( fill and drain). Filling port located upper position while drain is lower.
Inject your oil and check your deep stick after run your engine for minutes. Repeat those steps till you get normal level of oil. Never exceed max level of your gear oil.

it sounds like the rear engine oil seal is leaking check the breather on the engine to see if its blocked that could cause oil leaks from a build up of pressure

The gear box and the engine are separated by a clutch and flywheel in the manual and a torque converter in an automatic so I am little puzzled as to how water (presumably engine coolant) got into the gear box. That aside, the only remedy is to drain the gear box and replenish with new oil.
On the other hand do you mean that water is the engine oil if so this will need to be drained and renewed. The only source of water contamination in the engine oil, other than the inadvertent adding of water via the oil filler cap, would be a cylinder head gasket failure allowing water to leak from the internal passages into the oil ways. If that is the case the gasket will need replacing.

Change the gear oil. If the gear oil is leaking get it fixed as soon as possible. If all the oil has leaked then it may have severely damaged the gear box.