This question comes up often. If your 944 is an 87 or later it came with the updated water pump. Most of the earlier cars have them too because Porsche experienced a lot of trouble with cam belt failures in the early years and issued a Technical Service Bulletin (TSB). That TSB advised dealerships to install only the updated pump. The TSB came out in 85 but applied to all 944s.
TSB does not mean warranty. It just means that if water pump change is needed, the old style pumps are not to be installed.
OK so what does the new pump look like? A few pictures say it all.
My 2 cents - never, ever install an old style water pump.