Let's come up with an amphibian race!

Well, for example... it would be better if the hero created them... instead of summoning them...

Another imbalance. Creating something should cost money. Why can a ship be summoned if it's nearby, but a horse can only be created?

Added after 1 minute

These will be magical steeds. They always come when called. A ship appearing out of nowhere doesn't surprise anyone.

Distance should also be taken into account. If it isn't, it will be unfair to land-based heroes.