Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your fellow is experiencing a strange wheezing sort of cough and seems a little warm after a swim at the beach and eating a tennis ball.
I don't necessarily believe that he aspirated the water, but he may have swallowed enough to cause an upset stomach and some gastroesophageal reflux. Likewise the fuzz from a tennis ball is unlikely to create respiratory symptoms, but eating a tennis ball can cause stomach upset, reflux and possibly a gastrointestinal blockage which could cause what you are seeing as well.
Gastroesophageal reflux can cause excessive swallowing, and a sort of gagging/wheezing cough.
Is he eating normally today?
Is he passing normal stools?
If he isn't vomiting and is passing stools then we can try some things at home to try and settle his stomach and see if we can get him feeling better.
You can try using acid reducing medications to see if they help by decreasing esophageal burn and reflux. You can use either:
1) Pepcid-ac (famotidine) at one 10mg tab per 20 to 40 pounds of body weight every 12 hours
2) Prilosec (omeprazole) at one 20mg tab per 40 to 80 pounds of body weight every 24 hours.
These are acid reducers and may help settle his stomach and decrease the reflux if this is related to gastroesophageal reflux. They are very safe and can be used as needed with him.
I would start a bland diet of 1/3 boiled, lean hamburger (or boiled, white skinless chicken), all fats and juices drained off the meat, mixed with 2/3 boiled, plain white rice. Feed several small meals a day. You might wish to add 2 tablespoon of canned pumpkin to each meal for fiber to help him pass the tennis ball pieces.
If he's not significantly better in 24 hours, starts vomiting, refuses to eat, or has a fever higher than 103.5F then he needs to see his veterinarian.
Please let me know if you have any further questions.