I am a bit curious and this is off-topic but the question springs to mind - do all of your kids' baths always consist of - "baths"? Meaning the whole - filling the tub to a level, letting them soak for a while and then taking them out? How long do you let your babies soak? And after they are done in the bath - but are still covered in bubbles (and dirty water) - what do you do then? Do you run them through the shower before towelling off? I am kind of baffled.
I "bathe" (as in WASH) DD1 (5) about 5 or 6 times a week, mostly she has a shower with me or DP, sometimes she has a bath with the baby. The baby (11months) has a bath about (i'm embarrassed to type this!) once every 10 days! More often if she gets into something stinky of course, and i spend most of every day wiping mess off of her....
When i bathe them i put about 4-6 inches of water into the tub - enough so that sat in it it covers the baby's little butt, but not so much that if she fell on her back it would cover her face. I put her in, using a wee jug to wet her, wash her hair and body (i use a calendula hair-and-body-wash from Weleda), rinse her off and then let her sit for a moment if DD1 is in there with her and wants to play. I NEVER leave them alone, for a minute or a second. For me DD2 is in MORE danger with her sister there than alone. When DD2 is alone in the tub i kneel next to it, when DD1 is with her i physically keep a hand on her too. A 5yo is just so apt to splash and wriggle and a wee baby can so easily be knocked over. Then i take DD2 out, wrap her in a towel and take her to get her dressed, leaving DD1 in the tub. DD1 is then allowed to add hot water if she likes (she has been shown how to use the taps to avoid scalding, though it is theoretically possible it's hard to do with our water system as it's a combi and there's a temp limiter, so you have to turn the hot on full to fire the boiler and then turn it down a tiny bit at a time until you reach the line between maximum temperature and the flow being low enough that the boiler stops heating again). She is loud and we continue to talk while i deal with the baby. Then i go back in to brush all the teeth and take the plug out for DD1, who then gets out, dries off and puts her PJs on.
We don't use anything but the body wash on either of them in the bath because DD1 has very sensitive skin, and a bubble bath would make her so dry and itchy she'd be scratching herself raw all night. And the water isn't generally "dirty" because they're not usually that messy - if DD1 is actually muddy or sick or anything we use the shower.