That'll do for now I think.
Blastoise: Heavy armoured terrapin/tortoise, with the face of a Snapping Turtle. The jets are based on the Mollusc Siphon(cephalopods mostly), and the muscle tissue can extend, harden and rotate so water pressure and accuracy is increased (in before dick joke). The thing is, these siphons are very vulnerable compared to the rest of Blastoise's armour, so many trainers incorporate metals plates for protection.
Feraligatr: Saltwater Crocodile mixed in with the Kaprosuchus.
Swampert: Giant Salamander + Mudskipper + Axolotl.
Empoleon: Emperor Penguin + Rockhopper Penguin. Down sized the flippers as well. The sharp edges are hardened bone maybe?
Samurott: Sea Lion and Sea Otter. Samurott's back half needed more otter type physiology because a full fledged Sea Lion didn't work out. The head shell is based on a Caltrop Murex shell.