The Bridge Troll and Dire Bridge Troll

My first homebrew monster! This guy is based on the stats for a vanilla troll and I tweaked for my currently level three player party. The Bridge Troll hides in bodies of water (it can breathe normally or through adapted gills) or dark ditches and uses a tremorsense to tell when unsuspecting prey travels across it's naturally camouflaged crown (DC 25 perception or 21 investigation to spot it). It loses the Troll's bite attack but gains a Slam, using it's head like a hammer. The Slam targets a space and triggers a DC14 Dexterity save in a 10 foot radius around the origin point. The target takes 2d6+4 bludgeoning damage and any creature within the Slam's area of effect that fails the save falls prone.

I think that's everything I changed from the Monster Manual troll. My players had a fun tense time fighting it, and I realized I managed to actually sell them on loving the rental horse I gave them when the troll attacked it as easy prey.