Yes, a seating ledge is fine, and actually gets you points for accessibility in addition to making it more comfortable to lounge in the tub. I had one a few homes ago and there was no problem with water getting out.

I found a photo online that may help you.
I think the ledge is a nice idea, although flat w/tub.
Not raised like this one.
You might want to consider tiling the tub surround.

If you can find the post on "building a home" from beaglesdoitbetter's reveal -- shows a clever storage cabinet at the end of the bathtub.

writersblock - Thanks. I had thought about doing a shelves, but figured by the time we frame it in there wouldn't be much space left for shelves.

biochem101 - Yes, that is was I was thinking (minus the ledge across the back). The seat will be have to be raised though because this is not a drop in tub. Yes I wlll be tiling the tub surround.

RMSAustin - Oh, that is nice, but out of my skill set :)

Will you be having a shower curtain or shower door? If so, you might want to think about constructing the area in a way that you can use a "normal" size curtain or door. If your opening is larger than normal, you can expect to pay a lot more for your curtain or door. Just something to think about.

We have this. It's not my house, but a rental we live in while we're building.

We use it to store our bottles cause there are no other shelves in the shower. You can't pull the curtain far enough over to hide this, which is unfortunate. But water doesn't get out of the shower in this direction.

I've never used it as a seat because our tub is shallow so the shelf is pretty low to the ground. I wish it were a little bit wider so we could store our baby tub there, but it's not quite big enough.

The shower rod, which I'm assuming is a standard size, is stretched out to its max. I don't think there is quite enough tension on it. So I have to be really careful that the baby doesn't tug on it or it would probably pull down pretty easily. I would suggest a permanently mounted shower rod if you do this, not a tension bar.

Here's a photo. Sorry for the mess! HTH!

the ledge would be good. good place to put shampoo etc. or to sit with a basin of rather hot water on the tub floor to soak feet. If you have a hand held shower head you could keep it close to add more hot water as needed.

or build in a wall of shelves that face into the tub area for shampoo, soap etc with a cab at the outer end of it (facing into the room) for shallow storage - like extra shampoo, creams, lotions, bars of soak, epson salts (yeah!), even rolls of tp. or you could just do decorative shelves facing into the room - or a combination of the 2. Part storage w/a door and part shelves for pretty things - candles, dish of scented soaps, kleenex (not so pretty but good to have handy).

cottonpenny - Yes, this is what I was trying to describe doing. But ours would be higher for seat height.

Next question. Would you tile the seat or use something else like a solid piece of corian?

Some pictures I found.

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[traditional bathroom design[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by other metros media and blogs donna reyne jenkins

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Do it! This is one of the regrets I have from building my house. In my boys tub my builder wanted me to install my tub far down to the right and use the space to create a shelf on the far left end and tile it. Much like the 3rd picture that aa posted. I nixed the idea, because I was afraid they would get water everywhere.

I had to install a shampoo dispenser because I have no place to keep bottles or soap in that shower. That shelf would have been perfect.

We have ledge next to one of the bath tub. We will remove it in our upcoming remodeling.

The problem is when cleaning the bath tub and dedge, water flows down along the side of ledger and lands on the floor, instead of flowing into bath tub.

Putting things on it make the bathroom looks cluttered. It is too narrow to be a comfortable seat.