Ookay, I'm new to the forums, but I've hailed the Psydex as my greatest guide in catching them all in Pokémon Diamond. However, the other night I discovered that lapras can be found in the wild which blew my mind because as far as I know that's never happened before...
Anywho, there's a point to this post, when I couldn't find myself a lapras, I came online to Psypoke and the amazing Psydex for help, which told me that wild lapras were found on B1F of Victory Road, however this hasn't helped me because I still haven't found one. I think it's because the Psydex says B1F (Deep)... I have no idea what it means by "deep" so I'm probably looking in thw wrong place.

Can anyone please help me?
xox

either: a) use dive to go underwater or b) go deep, as in far into, the b1f of Victory Road ?

Exactly. The naming conventions for D/P Areas is a little odd. What it means (to the best of my knowledge, at least) is that you have to work your way all the way to the back of the first basement level; as far from the ladder that got you down there as you can be. There's obviously got to be somewhere to surf there, so that would be a good sign. Even then, only at 10% chance.