I think I will use mozzie deterents (but not DEET) and take the required anti-malarial drug (not Lariam) at the end of the dive trip.
HI
Everyone has this thing against DEET, but boy is it preferable to malaria (speaking as someone who has had the disease). As Drew says "DEET, treated nets and prophylactics are the WHO recommended preventative measures"
Ultrathon was mentioned, it looks weak at only 30% DEET, but it is the US Armys choice of repellent. The main trick here is that it comes as a lotion, applied all over like sunblock, and lasts 12hours (delayed release microcapsule or some such tosh) and is water resistant. I used this for two weeks in Roatan (No-see-ums territory) and didn't get one bite. On the last day, I was sitting around waiting for the ride to the airport and hadn't put any on (I was going home after all) and in 2 hours got bitten to pieces - so my trial of one proves Ultrathons effectiveness beyond doubt.
Don't dive on Larium, about 30% of people experience sleep disturbance of one type or another, this makes your judgment under stress less than perfect. More worrying if you have an underlying borderline psychiatric disorder Larium can make it manifest (remember Obsession is a psychiatric disorder - with like dive gear etc), and underwater would be a really bad place to become clinically paranoid.
As everyone says speak to the CDC / local travel clinic about what is right for you. Take the medicine AS PRESCRIBED for the DURATION PRESCRIBED (before, during and after your trip)
Cheers
Hal
(P.S. I am a physician who used to live in Swaziland, and dive in MZB and SA)