I have decode the stone slab under Vermilion City's water and got something like this:
t85 s53r5t (top secret???)
op5ns w85n
49v9n7 w9t8
wa9lord and (wailord and)
relicant8 (relicanth)
Can some1 tell what the remaining letter mean, i can't figure it out.
P/s: i like it how a lot of Gintama characters appear at Valencia Island, but i can't find Gintoki anywhere, did anyone find him yet?
The secret opens when diving with Wailord and Relicanth
Unlike on RSE, the order here is irrelevant. You just have to have them with you. Anyway, you'll have to wait for the next beta, because the door will open but the game will freeze when you're about to face Registeel
As for Relicanth, you can catch him underwater (near the dead boat site, I think)