Hope is fading for a teenage boy missing on the Victorian coast as a search enters a fifth day.

The 14-year-old went missing at Cape Bridgewater on Tuesday night after he and a 15-year-old friend were hit by a large wave while swimming in a rock pool and were sucked out into the ocean.

The other boy clung to a rock before he scrambled to shore, but his missing mate was washed further out.

While the boy was wearing a wetsuit and had good swimming skills, rescue efforts have been hampered by rough conditions.

Officers from the Victoria Police Air Wing will search the coastline on Saturday afternoon.

“Sadly, due to the passage of time since the incident and extreme environmental conditions of the area, police hold grave concerns for the welfare of the boy,” police said in a statement.

“Officers have been in constant contact with the family regarding the search which has now moved from an active search into a search and recovery phase.”

-AAP