Looks like the dolphin (second version) connects to a Technic axle, according to https://rebrickable.com/search/?q=6228&s...=all#parts while the first version missed the axle holder (rebrickable photo is clear enough).
Seems to be able to fit a 1x2 brick:
And in LDD, the dolphin does connect to a 1x2 brick, but not to an axle...
Attached the LDD mesh.
Seems to be able to fit a 1x2 brick:
And in LDD, the dolphin does connect to a 1x2 brick, but not to an axle...
Attached the LDD mesh.