Lily 3 Rechargeable Waterproof Personal Massager - by LELO
Petite, fully waterproof, and quietly capable — ten settings in something small enough to travel without announcing itself.
Dr. Zoe's Notes on How to UseDown Arrow
If you're new to this and you don't know where to start, start here. It's the one I recommend most often — small, straightforward, and not remotely intimidating to pick up for the first time.
The full IPX7 waterproofing is the detail I'd point out. It isn't only about the bath — it means you can wash the whole thing properly rather than wiping it down, and that matters more than most people realize.