Cross training challenge - need your input!

It's nearing month-end, and I need to find a new-to-me cross training activity to keep up with Kim at (Just) Trying is for Little Girls and her cross training challenge.

Source: loseweight-safe
via Myra on Pinterest

So far I've done cardio kickboxing and burpees. Over the summer I want to add stand-up paddleboarding to my list, but this month's travel schedule (racing in New Orleans, followed by a 5k in Pensacola, then spending a week in San Diego) made that a bit difficult to schedule. So I'm planning paddleboarding for my April new-to-me challenge.

In the meantime, I have 5 days to find and DO something new.

So, folks...
What new cross-training should I try? (And why do you recommend it?)