Can you transfer from the US submarine force to the surface fleet?

Unfortunately, yes. It actually happened to me just prior to my discharge. I was a Submarine Sonar Tech (STS1/SS) for 8 years, but was medically DQ'd for Asthma as a result of 5 years of submarine duty. I was approached by the Surface community to enter a new Intel program based on long-standing techniques used by Submarine Sonarman. I agreed, but eventually it took too long and I opted to get out. My rate was changed from STS to STG (surface) just prior to my getting out.

It actually worked out though. The person who hired me was a Naval Reserve Commander, and he and a Project Manager in the office recruited me into their CNO unit at the Pentagon. It took a SecNav waiver to open a billet for me (there isn't much need for Sonarmen at the Pentagon) and joined the Assistant CNO (Surface Warfare) as Program Manager for ASW/EW/C3 systems. I actually wound up writing training programs and policy for the program that I had been tapped for while on Active Duty. I even bit the bullet and did a 2 week underway on a Reserve Frigate. Of course it was going to Bermuda, so....

The Submarine Force is an all-volunteer force, and you can "un-volunteer" at any time, though if your rate is submarine specific like mine it can be sticky once you leave. To be perfectly honest, until I worked for and obtained my 1st Dan in Tang Soo Do Karate, I never felt the teamwork and camaraderie that is unique to the submarine community. Submariners respect ability and knowledge above all else first - rank is secondary. That's never been the case in the SW community.