I have a water resistant watch from timex i have been able to remove the back to replace the battery however getting the case back on is difficult.
it has an arrow on the back case which i used to prise the back off.
timex indiglo watch, metal case and bracelet.
you need to use a watch press. If you do not have a watch press you could take it to a watch repairer they may replace it free or for a small charge.You can do it yourself if you have a vice and two socket wrenches one small enough to fit on the back plate and one big enough to go over the front of the watch without touching the glass fiddly but do-able.
watchfixer, January 2013
On very tight ones, I use a metal ring one side, around the glass face as you do not want to break it, then I use a G clamp, or vice with a flat piece of aluminium against the back, slowly tighten clamp until you hear it click
