Fill the space between the sea and the horizon

Hello every body i guess this is a stupid question , but i have not idea how fill the space between the a and the orizon of the hdri image can some one tell me wher i can find a tutorial


You may be better off setting the ‘film’ to transparent so that the HDRI doesn’t show in the render, and then use an image plane of a sky as your background. Push the image far into the distance then extend your sea (may want to make it low res) into the distance until they meet (or until perspective bridges the gap). It’ll probably look quite odd, and quite sharp when they meet, so you’ll likely have to do some compositing.

In fact, if you can find an image that contains both sky and sea, it may work even better. Some DOF will help as well.

So every sea landscape ,is done with a plane image, when this problem occour?Is not possible use a hdri for lightn and backround?
Excuse my bad english: