I've been wondering what they are. A recent Port Marine Notice suggests they are a kind of 'Sea Barrier' and are made up of "marker buoys with sinkers and HDPE drums linked up with stainless steel chain." Another long series of these drums are planned for installation at Pasir Ris towards Pulau Serangoon.
I wonder if they will have an impact on the marine life on the shore?
Construction of Sea Barrier at Serangoon Harbour
from Port Marine Notice No. 06 of 2011 dated 25 Jan 2011
With effect from 08 Feb 2011 to 07 Aug 2011. 0800 to 1800hrs daily including Sundays and Public Holidays. Location : Serangoon Harbour and its vicinity (see attached chartlet):
The construction works will involve installation of marker buoys with sinkers and HDPE drums linked up with stainless steel chain. A safety boat will be deployed to advise all craft to keep clear of the working area. Further general enquiries relating to the project can be directed to Mr Bobby Woon, the project manager at Tel: 9456 6876 (email: firstname.lastname@example.org).