It often is overwhelming to learn that you or someone you love has a chronic illness. If your husband will need dialysis in the future, it might help to look at https://mydialysischoice.org/. This tool may help you and him decide which dialysis option best fits your family's lifestyle and values.
You ask how he can look healthy and be sick. People who have kidney disease may not notice the symptoms in the early stages and some symptoms they do have can be attributed to things like the flu or even feeling overworked. You can read about the symptoms of kidney disease in Module 1 on Kidney School. You can also read about treatment options in Module 2. Module 5 may provide tips that can help you and your husband cope with kidney disease. There are 16 modules in Kidney School. Hopefully some of them will help. http://kidneyschool.org/mods/
If he believes peritoneal dialysis is the best fit, it's best to get a PD catheter placed a few weeks before dialysis is needed. This will allow time for the exit site to heal so training can be started and he can avoid a hospital stay. So far as swimming, talk with the doctor and home training nurse about swimming with a PD catheter. A textbook written by nephrologists who are PD experts suggests that once the catheter has healed assuming there is no infection, it's OK to swim in chlorinated private pools and in the ocean as long as the beach where your husband swims isn't in a highly populated area or near a sewage outlet where sewage is dumped into the ocean. However, it's very risky and not recommended to swim in lakes, ponds or public pools. Your husband can ask the doctor or home training nurse about special bandages to use when swimming. Here's the link to the page in the text book that talks about swimming. https://books.google.com/books?id=hSkN5rbg6o0C&pg=PA361&lpg=PA361&dq#v
There are 3 types of vascular accesses - fistula, graft and catheter. The best vascular access for hemodialysis is a fistula because it usually lasts longer, performs well, and has a lower risk of infection. It an take several weeks to months for a fistula to develop. Some people's blood vessels won't support a fistula and they can get a graft. A graft hooks an artery and vein together using artificial material. It requires a shorter time from surgery to use, but doesn't usually last as long and has a somewhat higher infection risk than a fistula. A HD catheter should be avoid as much as possible and only be used if dialysis is needed emergently. Catheters go into a major vessel in the heart and has the highest risk of infection. HD catheters don't work as well as fistulas or grafts so they may not allow the best removal of waste products from the blood during dialysis. If you use the Kidney School link above, Module 8 is on vascular access and might answer your questions.
There are things that can be done to slow the how fast kidney disease progresses including changes to medications, diet, etc. If he's in chronic kidney disease Stage 4, your husband's insurance may cover getting advice from a dietitian who provides medical nutrition therapy (Medicare covers this). If you have kidney disease classes in your area, they can help. If not, Medical Education Institute who operates this website created a series of presentations entitled "How to Have a Good Future with Kidney Disease" that you can access here - https://lifeoptions.org/resource-library/good-future-patients/.
Finally, he may be a good candidate for a transplant. People can be evaluated now and get a transplant as soon as when kidney function is 20% or less. Some people are able to avoid dialysis, especially if they have a willing kidney donor. Patients can self-refer to transplant programs. He may want to find out where his insurance would pay for a kidney transplant. This database allows you and your husband to check out area transplant programs' outcomes. Choose "kidney" for the organ and enter your zip code to get programs within 50 or more miles from you. https://www.srtr.org/transplant-centers/
You may also want to be aware of the Home Dialysis Central Facebook group. There are several thousand patients and dialysis staff who post regularly to that closed group to get support and their questions answered and . You have to request to join and no one outside the group can see what you write there. https://www.facebook.com/groups/HomeDialysisCentral/