i first took melissa swimming at 2 months. but theres no age limit i dont think, just as long as they can support their head.
yeah use swim nappiess with a swimsuit over the top.
my tips are: use huggies "little swimmers" swim nappies coz when wet u can just tear the sides off. i used boots own at first and millie used to cry when i pulled them down coz they tight and wet dragging against skin etc.
oh, and dragging wet swimming costumes off upsets them too- so my strategy now is to remove the costume while still in the water (not the swim nappy tho) it slides off more easily. (stuff it down ur cleavage, lol dont hang the straps off ur arm coz might catch on somethin and u might slip with baby- scarey thought, gotta be cautious!)
prepare for lotsa standing shivering freezing in ur wet costume while u deal with the number 1 priority- getting baby warm and dry first!
and one or two having to dry urself with a towel covered in piss
(i take 2 big towels and 2 small ones but millie uses them all first coz the changing table is hard plastic, like to make it cosy for her lol)
it is lovely swimming with them tho. hope u both enjoy it