Horrifying moment seaplane crashes on Rottnest Island captured by witnesses on beach

Beachgoers have captured the horrifying moment a seaplane crashed during takeoff just off WA’s Rottnest Island.

Vision from the shoreline shows the plane building speed and slowly lifting off before dipping left where its wingtip breaks the water, sending the aircraft’s nose slamming into the ocean.

WATCH THE VIDEO ABOVE: Moment seaplane crashes off WA’s island paradise.

WA Police Commissioner Col Blanch said it appeared the plane had hit Phillip Rock near the entrance to Thomson Bay about 4pm on Tuesday.

Witness Anna Connolly had gone to the beach for a swim and said the plane struggled to take off.

“It took ages to get off the water but then right towards the end it just really didn’t look (good),” she told 7NEWS.

“We had a feeling, everyone thought something was wrong, it didn’t look very good at all.”

Bella Rawlings was with Connolly and said that once the wind got under the wing it “picked it up and nose-dived it into the water”.

Police confirmed seven people, including a pilot, were on board at the time of the crash.

Four people were recovered from the water, with three people taken to hospital “with varying levels of serious injuries”. The fourth person was uninjured.

There a grave fears for the remaining three who are unaccounted for.