Aah, love the colors here, and your mountains are amazing, Abu !
Just... I wonder if there is not a small perspective trouble, as if the coastline sounds like top view but mountains side view, if it makes sense ?

I maybe have some tips for you, but it's difficult to say in English as painting vocabulary is very specific... :
For the sea, if you use a good watercolor paper you should try to moisten the paper first and apply the color when it's still humid/wet. It needs some practice to success (and depends on temperature, etc...), but that's the joy of watercolors ^^'
Generally speaking, if you use slightly more water, you should be able to make smoother junctions as your paint will not dry that quickly. Using two brushes could help too : a big one with water for applying large flat color, and a smaller and dry one you can use to "push" the color along the borders or to make lovely gradients : needs to work quickly, but I saw some watercolorists using both brushes in the same hand