Two points. The water running through the middle looks like a river which is odd - I know that might have been part of the shape but you cant reasonably have a river connecting two seas. We have oodles of posts about rivers here so its a common theme. The next one id suggest is that it looks like the island is sunken into the sea. This is because the shadowing light source is from the bottom right to top left. If you place the light source top left and shine to bottom right it flips it over so that the island looks raised over the sea bed. Its because were all used to the sun being above us so stuff looks right if lit from above. You dont have to take the advice but if you try it I am sure you will see what I mean. Otherwise I thought it was a great start to your maps here - and welcome btw.