Doctors do not usually speak of "water on the heart." The closest possibility is known as a "pericardial effusion." I bet what was meant is a pericardial effusion. Pericardial effusion, sometimes referred to as "fluid around the heart," is the abnormal build-up of excess fluid that develops between the pericardium, the lining of the heart, and the heart itself.
Pericardial effusion, and the possible inflammation of the pericardium resulting from it (called pericarditis), can have many possible causes, including:
Infection such as viral, bacterial or tuberculous
Inflammatory disorders, such as lupus
Cancer that has spread (metastasized) to the pericardium
Kidney failure with excessive blood levels of nitrogen
The seriousness of the condition depends on the primary cause and size of the effusion and whether it can be treated effectively. Causes that can be treated or controlled, such as an infection due to a virus or heart failure, allows the patient to be effectively treated and remain free of pericardial effusions. Pericardial effusion caused by other conditions, such as cancer, is very serious and should be diagnosed and treated promptly. Additionally, rapid fluid accumulation in the pericardium can cause cardiac tamponade, a severe compression of the heart that impairs its ability to function. Cardiac tamponade resulting from pericardial effusion can be life-threatening.
Treatment of pericardial effusion is based on the underlying condition that is causing it and if the effusion is leading to severe symptoms, such as shortness of breath or difficulty breathing.
Depending on the cause, the excess fluid may be either rich in protein (exudate) or watery (transudate). These two categories help physicians determine the best way to treat the cause of a pericardial effusion.
It is possible your Dad has congestive heart failure, causing fluid retention. The fluid can build up in the lungs when the heart's pumping ability is weakened by previous heart attacks or coronary artery disease, etc. The water isn't really "on the heart" but building up in the body because the heart is weak. The shortness of breath should subside as the diurectics get rid of the excess fluid. I would also wonder about his kidney function if he is very anemic. The cause of his anemia should be sought, as that will worsen congestive heart failure by making the heart beat faster. He does sound sick, but CHF is very common, and in most cases can be treated with medications and stabilized. I would speak with his Dr and try to get as much info as you can. You can also ask your Dad why he has been giving you money. If he thinks he is dying, he may be trying to take care of his financial matters in advance. Hopefully, he will be honest with you. His feelings should be taken seriously, as people often know when their time is near. Hopefully, that is not the case, but better to know and be open about it with each other.