User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-765166-20140712231844/@comment-1011548-20140713103105

There's definitely no underwater combat.

In 3 Ultimate I kinda got the impression that Ivory Lagia was a sub they could bring back in future back if they wanted to feature Lagia but didn't have underwater stuff. Obviously Abyssal you could never have, but normal Lagia is pretty dependant on water too, IMO, and much easier out of it. Hence a land-based Lagia sub.

tl;dr - I think there's a chance (a small one) that Ivory Lagia is in 4U. But obviously we can't confirm it just from equipment.