-1 echoes of the beast (echolocation)
-1 aquatic (technically a dolphin can drown... but in terms of game mechanics this is close enough.)
+0 truly aquatic - a dolphin out of water is not long for this world.  But, as Johann can shapeshift, this isn't worth any refresh to him - and he's been known to make (brief) use of the form out of water on occasion anyway, mostly when he needs its sonar to diagnose internal injuries in someone else.
-2 Inhuman Speed
-4 supernatural recovery
+3 catch
-1 ramming speed (fists attacks at weapon: 2 against unarmored targets, or weapon: 1 against lightly armored targets; a dolphin may not have the world's greatest selection of natural weaponry, but their noses do make decent battering rams.)
-1 flesh is transparent (conduct medical diagnoses with no penalties for lack of x-ray or nmri type equipment; a dolphin's sonar can pick up on subtle things like early-stage cancer that even a full medical lab would have difficulty pinning down.  On the other hand, this ability offers no advantage to diagnosing purely chemical issues.)
-1 only half asleep (no penalty to alertness when sleeping; dolphins sleep half their brain at a time so that they don't drown)
-1 wave-dancer (+2 athletics when sprinting; a dolphin can keep up with ordinary ships for at least a while, though it can't match an actual powered racing vessel.)
-1 electroreception : the costero dolphin species has this extra sense, and I had enough spare refresh to just buy it as a supernatural sense.  In the form of the other dolphin species Johann has access to, this ability is not present (but is still paid for, so that he can shift between dolphin species as a supplemental action.)

(unspent: +1)
+6: 
+5: scholarship, alertness, investigation
+4: athletics, empathy, lore
+3: conviction, presence, fists, endurance
+2: rapport, might, discipline, survival
+1: performance, stealth, deceit, contacts

details on individual forms:
Johann has access to one male and female form of each of the following three species:
common bottlenose dolphin - an ocean-dwelling dolphin that's quite capable of swimming around the world; this is also the current popular image of a dolphin due to its use in captive dolphin shows.
short-beaked common dolphin - more adapted to life in a continental shelf area, but also featuring a world-wide species range.  This is actually a more common species than the bottlenose dolphin, with a distinct multi-colored appearance (dark top, light bottom), and matches well to most ancient portrayals of dolphins.
costero (sotalia guianensis) - lives in the amazon river basin & coastal areas; capable of tolerating long-term exposure to both fresh & salt water.  Plus electroreceptive ability, which is just neat.  Similar in appearance to the bottlenose dolphin, aside from the pits along its nose that house the electroreceptors.