I suspect that engines water pump seized.

Your question isn't very clear. You said the engine has seized, then you asked if the water pump seized.

Seized water pump is not very likely. When the bearings go bad, the shaft wobbles resulting in a damaged timing belt. Usually you'll have coolant leaking before it gets that bad. If the timing belt jumps a few teeth, this is an interference engine so the open valves would block the free movement of the pistons. It's hard to say when the vehicle has been sitting for a long time, but if you can look at the timing belt and timing marks, start with that. If it looks like the belt might still be in time, the valves should be okay. If the crankshaft is about a third of a revolution from top dead center, there should be no valves that are fully open. At that point you can remove the belt and try to turn the crankshaft by hand. If you can't because a piston is hitting a valve, you WILL be able to rotate the crank backward at least a little before it locks up again. If the piston rings are rusted to the cylinder walls, you won't be able to turn the crank even a little. For that, remove the spark plugs, then pour in about a tablespoon or two of diesel fuel into each cylinder. Diesel fuel is a lubricant and will free up stuck piston rings. Give it a couple of days to do its magic.

Just saw your second post. Once you get the crankshaft to turn, you can perform a cylinder leakage test if you can find a tester. Check at an auto parts store. Many of them rent or borrow tools and they might have one.

You put the crankshaft at top dead center for the cylinder you want to test. That's easy to find for cylinder number one. For the rest, you can screw a whistle into the spark plug hole. It will whistle while the piston is coming up on top dead center for the compression stroke. Stop turning the crank when the whistling stops. Screw the tester's hose into the spark plug hole, then connect it to a compressed air source. Air will be forced into the cylinder at about 30 psi, then you can observe the percent leakage and check in four places to determine what is leaking. If a head gasket is leaking you'll see bubbles in the radiator or in your case, you might be able to hear the hiss through a radiator hose.

The other sources of leakage are an intake valve, (hissing at the throttle body), exhaust valve, (hissing at the tail pipe), and the piston rings, (hissing at the oil cap or dip stick tube). This is a much more informative test once a compression test has indicated there's a problem. Also, a leak in a head gasket can be way too small to have an adverse effect on a compression reading.