If you switch from Army to Navy, would you have to go through Navy basic training?

Normally the Navy does not take prior service. But hings do change.

Best thing would be to contact a Navy Recruiter to find out specifics. If i remember right years ago, Other Service Vets (OSVETS) went through an abbreviated boot camp (4 wks i think). Mainly it was for uniform issue, familiarization with Navy regulations and terminologies and to learn shipboard fire fighting and damage control. I'm guessing things have changed quite a bit since then .

Beginning and ending of possible advice: Talk to a recruiter. That said, Navy boot camp does things no other services do except the CG. Teach you how to swim through burning oil, and basic firefighting, for example. So I'm pretty sure you'd have to go.