Could get a play mat and do some tummy time, I also had a water mat and it had little fish in it that move about, my son loved his, lasted til he was about 12 months old until he popped it 😂🙈 https://amzn.eu/d/7D6w6PJ
Use play mats, seats and tummy time mats. Have a sing song, read a book at night. Bath a baby also before bedtime. Go out for a walk (sometimes we take baby shopping during wake windows but mine is 5 months so goes longer without feeds). Go out to a cafe or socialise (babies love socialising). Play with toys. Talk to them. Baby groups. Baby massage or yoga. Clean when wearing baby (no chemicals, hot stuff or anything slippery though). Sometimes it’s good to leave baby to their own devices and give them a toy or two and let them babble to themselves.
We did mats, books, high-contrast images, and tummy time at that age, no screen time. Screens keep their interest because it's all flashing lights but they learn most at that age from interacting directly with people and from exploring the world as their sight improves. That's why high-contrast images are so great now, they can see them easier! Download The Wonder Weeks app for ideas or you can look into subscriptions like Lovevery or KiwiCo, or Tiny Land on Amazon has months-of-age boxes that you can get without a subscription.
I would really advise you not to do any screen time until they’re 2 years old because their brain I still just developing and it’s not the best. I put toys that make noise in front of her and tummy time but at this age she doesn’t interact much yet
We had the finding nemo play mat which lights up and sings my son used to love it but only if I laid next to him! Here’s the link, we found ours at a Bootfair and got ours for £5 and I see them fb marketplace too https://amzn.to/4etY9NT