"家から海が見えます。" is correct, because you want to say you "can". "家から海を見ることがあります。" shows just the fact that sometimes you see the sea.

"家から素敵な海が見えます。" "My house has a fabulous view of the sea." "私はとても疲れている時に海を見ることがあります" "I have a view of sea from time to time when I am so tired." or "I will often see the sea ..." Hope this helps.

There are several similar sentences. I can see the from my house. = 家から海が見えます / 家から海を見ることができます。 *in this case, you cannot say 見ることがあります in the basic translation, however, on the subtitles or something, they can say so depending on the situation. Sometimes I can see the sea from my house. = ときどき家から海を見ることができます (or 見ることがあります)。 Sometimes (I have opportunity that) I can see the sea from my house. = ときどき家から海が見えることがあります。 *There are more translations and I wrote the basic one. I hope this helps you.