RE: Your throwable type 4
A friend of mine is a commercial as well as recreational diver.
He had his arm broken trying to get back aboard.
The wind came up while underwater and the swim step hit him as the waves caused it to rise and fall.
*A swim step can be dangerous in some instances.
Now he always make sure the dink is in the water when he dives. Easyer to get into the dink if it ever happened again.