It's not that hard to make one that's better than almost anything you can buy, and ladders are unnecessary if you do it right. A friend of mine and I each made one like this for our Seafari's over 30 years ago.
Here's wife and daughter using it in the Abaco's in late '70's.
Bought an 8' length of stainless tubing and a 1" thick piece of teak; used a conduit bender on the tubing and his Shopsmith to cut the planks and drill the holes to mount the planks. Took us about 8 hrs to make 2 very nice and light half platforms. Mounted to transom using stainless bimini top fittings which allow it to fold up when not in use. Removal of 2 screws allowed it to be taken off for fishing. If you mount it correctly (right at the waterline, so it's just about awash when someone's on it; most swim platforms are mounted way too high!), you might not need a ladder. I did have a removable 3-step ladder I could use on this one when I had someone along not agile enough to get aboard w/o a ladder. If your wife and kids can get out of a pool w/o a ladder, they would not need one for this type of platform if you mount it right. For scuba, if you just take off tank in the water, you still don't need a ladder!