My little girl loves bath time and has since birth. Recently, however, she didn't want to stay in the bath for long enough to bath at all. We decided to add a few toys to bath time, and it's been a great success.
We bought a few different sets of Alex Rub a Dub Bath Tub Stickers with numbers, shapes, animals and so on and now they pretty much live in the bath. They're made of thick and chunky foam, which makes them easy for little hands to grab onto and when wet they stick to the bath or the tiles, without leaving any residue when they come off.
The only negative to them is that eventually the ink fades, so the pictures become a bit light and start looking a little old, but my daughter certainly hasn't noticed.
The stickers can be packed away in the hanging bags that they come in, which is great for when you want to bath without floating bits in the water.
From an educational point of view they've been good too. My daughter can recognise quite a few of the shapes now. Say “bee” and she'll find the bee, upside down, with or without the picture. The same goes for 'wower' (flower) or “fish”. And every week the list gets longer.
They're not super cheap, but they're worth it, I think. We'll be adding to our collection soon.