Pool waterfalls can be created to look natural if done correctly. But...
Building waterfalls is our craft. If it is you desire to have your waterfall go into your pool, then we can do that.
If someone wants to have a pool waterfall, there are some special considerations involved (and usually added cost). I always recommend to not have the waterfall go into the pool for the following reasons.
The use of mortar and concrete is time consuming and adds more expense to the waterfall.
Pool waterfalls fall under the jurisdiction of "pool contractor". You need a special license to build pools, and because of this license, we will need to work in conjunction with your pool company.
Laws dictate how much suction you can put on your pool. Filters and hot tubs and water jets can take away precious water flow to the waterfall that will be only a trickle compared to a separate pondless waterfall.
Pool waterfalls generally look less natural than their pondless waterfall cousin.
The best time to put in a pool waterfall is during the initial construction of the pool. If it is done as an after thought it can take some serious pool configuration to get the correct water flow.
It is best to insist on making sure you will have the right water flow (a big enough pump). Me personally, I would insist on having a separate pump that is as large as code will allow for the pool waterfall. Nothing is worse to me than having to create a pool waterfall that will only trickle.
Some people enjoy only a trickle. So if you like a trickle and your pool contractor says what you have is enough then it probably will be.
If you are looking for that raging waterfall look it may take some persistence in the planning phase to make sure you will have enough flow.