Firstly as mentioned above a boat or kayak will make your journey a lot easier!!!
If you however really have the dying urge to burn off some excess energy and want to attempt it make sure you chat to the local fisherman and found out about the local currents and conditions. You may even be able to use some of the prevailing currents/tides to your advantage and do at least part of the trek as a drift dive? Before committing yourselves to the swim study the weather patterns well...the sea is unforgiving and shows no mercy. Check this site
Photography Blog - Roger Horrocks is a freelance photographer specialising in environmental and underwater photography for news, editorial, and read the section entitled marine trekking, these guys did something similar just over a greater distance with a bit more backup! I think it would be easier with this kind of setup even if only one or two of you tow necessities, which you'll invariably need. plus then there's a place to keep fish outa water.
Lastly I assume you guys are pretty much diving fit and ready to handle whatever surprises the sea can conjure up.
that's it for now..Goodluck!
