you need certain pokemon

YOU'LL NEED WAILORD AND RELICANTH

I already have both pokemon but where exactly the location of REGIS?

i dont know which regi is where but
go to desert (bottom entrance) go right and then down ta da
near dewford north
west of lilycove keep going you should se steps go up them and keep going up
p.s to unlock these caves go to pafdilog i dont know what its called sorry!! surf west and
you should find a place where you can dive

things you need:
wailord
relicanth
dig
strengh
fly
patience
pokemon lv50 - lv70