I just completed this very lengthy process. There is not a clear yes/no answer to this question.
First is the location of he land.
Second is are there other piers in that area.
Third is have your land neighbors already applied for and been approved but have not yet built?
The town council must approve the request, then then Ministry in Belmopan, then a final approval again by the town council.
The process took me about 8 months to complete while living here in the US. But I don't think living there would speed the process much as I hired three different locals all with "political connections" to help me. I also went personally to the contact person for the town council and also personally took the town inspector with my contractor to the site.
My contractor has lived and worked constuction on the island for over 30 years. He knows everyone and everyone knows and likes him.
Buy the land first, worry about the sea wall / pier later. The pier is "Queen's beach" or public property. Although some people have constructed gates/locks, they have done so illegally. If anyone wants to sit, fish or dock on your pier they have a right to do so.
If planning to build one in or very near to town you can pretty much forget it, you'll not likely to get approval. The local government wants to limit the concentration of piers.