It is! And not to be sniffed at. It is a proper adventure and you need to be well prepared.
If you limit to Part 91 and exclude helicopters... from NTSB data.
73% of ferry pilots that ditch survive the splash down and the sea survival.
87% of ditchings result in all souls saved.
93% of forced landings on land result in no fatalities though injuries including burns are a lot higher.
This is Paul Bertorelli on ditchings
http://www.equipped.com/ditchingmyths.htm
While in Australia I tracked down Ray Clamback to talk about his 300 or so deliveries from the US to Australia and New Zealand and his two open water ditchings
http://www.equipped.com/1199ditch.htm
That route is a probably the most typical avgas route to NZ though I think some are avoiding Cassidy these days as you have to position fuel there in advance. East is way, way harder from a handling, not getting shot down, mugged, ripped off, sold barrels of avgas full of water etc. perspective and a lot more expensive. You can go North and through Russia and Asia if range is limited but the water is much colder and land is not that much safer to land on in an engine out scenario.
Sea survival, temps, sea state, shipping movements, inReach PLBs and ground crews, tropical CBs, limited approach nav aids, Hobbits and real life Dragons you have to contend with Westbound. Believe it of not SEP can actually be safer then MEP when so tanked up that one engine will not keep you in the air even in ground effect for the first 1/4 of the leg.
Lots to think about, and a real achievement to get done safely, even with GPS.