OLTC - Ocean lifeguard training course

O-ring - A metal ring on the bow of a boat, used to tie the bow to the trailer (n)

oar - A lever used to move a rowboat (n)

oarlock - The combination of the thole pins and the wear blocks in a surfboat; the oar sits between the two metal pieces (n)

offshore - A wind blowing from the beach to the ocean (adj)

onshore - A wind blowing from the ocean to the beach (adj)

outside - On the ocean side of the surf line (adj)

over the falls - When someone riding a wave falls down the face and the wave falls on top of him or her