Hi trymixdiver,
With routine donation, only about 10 percent of targeted platelet cells are removed. Everything else is returned to the donor.
These platelets are completely replaced within 48 hours. The Red Cross will allow one to donate as often as every two days, but generally prefers that one not do so more than every two weeks. In any case, no more than 24 donations per year are allowed.
The important issue is that because no meaningful amount of red cells is removed, there will be no anemia or fatigue. It's also the reason that the Red Cross allows one to donate according to the guidelines above, while whole blood donations are limited to every 8 weeks, or no more than 6 per year.
Sources that I have been able to locate indicate that a donor may return to normal activities immediately, but should refrain from strenuous activity for 24 hours. As with whole blood donation, a diver needs to keep up with appropriate hydration & not dive if they're not feeling entirely up to it.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such. Speak with the professional overseeing your donation about any concerns you may have regarding donation & diving.
Platelet donation saves lives. Those who do so are to be commended.
Best of luck.
DocVikingo