It's worse to get FW tank water in your mouth. SW just tastes .. well .. salty. Besides, what doesn't kill you only makes you stronger ... right? Something like that anyhow.
Sometimes I use a syringe to start a drip siphon when acclimating someone. For water changes if you're using a siphon hose with a little flapper thing then all you have to do is give the tube a few shakes and the siphon starts.