By air it's maybe 10-12 miles to the coast. However, the
shortest path is very nearly exactly diagonal to the main street
grid, so it's closer to 15 or 16 miles driving distance.
It's roughly 15 miles in a straight line from Disneyland to the ocean (slightly more if you're driving and following the street grid). This is considerably closer to a coast than Disney World is, but it's not exactly "on the beach."