Can I go snorkeling 10 months after a hair transplant?

At 10 months, you can go snorkeling. If you are worried, it is best to contact your surgeon for post surgery issues and care since all doctors have slightly different instructions.

Yes you can pretty much do anything after 2 weeks post op let alone 10 months. Im not sure why you thought you had to ask about snorkeling at 10 months but rest assured you are fine. 

hi! transplanted hairs are pretty hardy so most hair transplant patients can resume usual activity within 3 months of the treatment

You may start to gym, heavy exercises, swimming and snorkeling 2 weeks after the FUE operation. Jogging, running, sauna, cycling snorkeling  don't give any harm after 2 weeks of operation 

Snorkeling or scuba diving this long after hair transplantation will not have any adverse effects on your grafts.