What is the best way to build a swim platform ?

Question

my boat is fibreglass

Answer 1

Unless you are a fiberglass technician, and have the environment to handle, the chemicals, fiberglass, epoxy, and gelcoat...

I would go with someting like this..

http://www.swim-platform.com/swim-platfo...

Answer 2

A lot of info is required to give an answer so can I suggest you check with your boat manufacturer to see if they have a proprietary one or at least see if they would recommend how to build one.