Originally Posted by
Dork_Forge
Anything that doesn't have a swim speed gets disadvantage on melee weapon attacks, so that would apply to the Beast of the Land as well.
Then there's the whole it not being able to breathe under water thing...
The Beast of the Sea is not useless when used in it's appropriate environment, underwater sections (and even whole adventures) are a thing, this is just an option for those occasions and not really intended to be used otherwise by the looks of it.
Though if pepole actually have a problem with this then just ask to drop the swim speed down a little and bump up the land speed accordingly...