What exactly does it mean when it is flooded does the computer stop working?
usually. It shorts out and fries the computer. corrosion will also occur overtime in the innards. IN short, remember that it is a dive
COMPUTER, emphasis on the word computer. If it (or your desk top or cell phone) get flooded, they get all prissy and usually stop working. Sometimes you can dry them out and they will work again. Salt water is really not a great thing for computers and the insides of a dive computer are not designed to get wet.
Also when I put it in the water the screen fills with water (still works and can see screen better) is this normal...
Unlikely that water is actually flooding the screen and it continues to work. Quick test. Put the thing in water, and see which of the following happen:
1. Screen floods instantly.
2. Screen clears instantly save for some water drops and fogging.
or does it
A. Screen floods slowly.
B. Screen drains off very slowly or not at all when removed from the water.
If 1 and 2 are correct then that is the lens protector water is getting behind, not the screen. It is suppose to do that. The screen protector is a piece of polycarbonate or plastic that is there to get scratched up and cracked by stuff it encounters and to protect the computer screen from suffering the injuries it will endure. It is user replaceable as it just (usually) pops in our out. It will get scratched up and when in the water with water filling in the scratches and behind the lens the scratches magically disappear. Another user posted photos of dive computers with their user replaceable lens protectors removed.
If A and B are correct, then you have a problem.
Take the dive computer to a local dive shop, many have small pressure chambers to test the computer in to ensure it is not leaking.
When you replaced the batteries did you buy a battery replacement kit and replace the O-rings? Did you remember to lube the O-rings with silicone grease and to ensure there was no dirt, sand, lint on the O-ring or on the area of the dive computer or cover plate that will contact it. A grain of stand or a cat hair on the O-ring could be all you need to flood it at depth.
Last but not least, go online to the mfg website and download the manual.
READ the manual! Then read it again and again. Practice with the dive computer. A dive computer you are not familiar with and know how to use and more importantly interpret what it is telling you is
dangerous. Not fully understanding your dive computer can cause you to misunderstand what the computer is telling you and to
ignore warnings or to miss-interpret routine normal information as you are in an emergency and reacting as such.
EXAMPLE 1: A dive buddy was miss-interpreting what their dive computer was telling them. The dive computer was saying they were at 15 feet, max depth 60 feet and it was at 1 minutes left on its count down of the safety stop time from 3 minutes with 750 PSI air remaining. They were miss-reading it as they were AT 60 feet and at 750 PSI and since they were navigationally challenged thought we were still 400 yards off shore. The Diver in question signaled me their air was 700 PSI and I signaled, OK understand 700 PSI. Long story short, the other diver kept signaling their air and was clearly getting worried and quite concerned that I was non-pulsed and continued to look at the fish and octopus. When we surfaced they were shocked to learn they were at 15 feet doing the safety stop and 20 feet from the dry sand of the beach. They thought they were still about 400 yards off shore and at 60 feet and were quite concerned. They were miss-reading the computer to be showing them and emergency where they were just fine.
EXAMPLE 2: On another dive at 100 feet a diver read their computer as having 19 minutes of No Decompression Limit time when they had been under water 19 minutes and needed to be heading for the surface as the remaining NDL was and could not understand why their dive buddy (me) was insistent they stop taking pictures and start up, now. I hope these two real life examples will serve to illustrate the necessity of understanding how to read and use your dive computer. Here they were miss-reading the dive computer to be showing them they were just fine when they needed to be heading for the surface.