similes and comparisons, What's the Rule?

[ScriptNurse]

As long as the description is accurate and visual, I see nothing wrong with it.

[cadence]

Hello
In the event of being expedient and direct in my sluglines I have been describing some actions as similes.

Is their anything taboo about it that I should know [other than don't do it to much] or is it ok?

Here is an a couple of examples
They move like stealth ninjas
He leaps off the edge and flays his arms like a base diving.

I'm particularly describing things that are not of this world and so a familiar comparison is helping me articulate with out a wordy entrail.

thanks for you insight