Risk is relative, just be aware, and prepared for the risks. I've done many extended over water single engined flights, never a problem. If the water is lass than "very warm", wear a dry immersion suit. If the water is "very warm" (which I doubt), wear a life jacket. Failure to wear the appropriate emergency apparel could be fatal. If you're unable/unwilling to wear it, don't fly it. If you can, take a raft. Pratice in the water in both the suits and with the raft if at all possible, they are not as easy to use well as you think. If you're flying with a partner, put the raft in a swimming pool, and practice getting in, it requires skill and coordination with your partner. Make sure you're visible, and have a suitable beacon. Carry everything you want out of the plane, on your person. If need be, in a water proof bag. If it's not on your person going out the door, you're likely not to have it at all. Even plan to get a raft out, perhaps from the passenger's lap. If the plane flips when it hits, you won't have time to search the cabin for things, you'll get yourself out with what you're carrying.
Flying higher is better, get as high as you're able, weather and ATC considered. Try to be in communication with someone, either ATC, or a relay aircraft all the way along. Know where you are (GPS lat/long), so if you so have a problem, you can tell someone where you are. File an accurate flight plan, then fly the route you planned - don't deviate, a search won't find you if they're looking in the wrong place. If the weather turns bad, tell someone, and turn around. Don't fly over water at night. Let alone being very hard to find if your ditch, overwater at night may as well be instrument flying (see JFK Jr.)
Get to know the water, and consider it as you're flying over. Identify waves and swells, they're different. If you must ditch, ditch along the swells, as into the wind as possible, but along a swell as the priority. Don't let the waves distract you, it's the swells which hurt if you hit them wrong.
There is lots written about ditching, so searches will turn up lots of useful information. There are also underwater egress courses, which are excellent training, and just plain fun!
As to risk, it's yours to consider. Different pilots have different risk thresholds, and that's perfectly okay. Just understand it, and be prepared if you decide to go. When I was crashed into the water by my fellow pilot two years ago, a lifetime of swimming, 25 years as a water and ice water rescuer and trainer, having been wearing my life jacket already, and warm water all contributed to it not being fatal. My friend, an 20 year water pilot flipped his floatplane 5 weeks ago, and drowned. Though an experienced pilot, he was unprepared for water entry. His wife and kids aboard survived. I like to think that if he had to drown, he did it helping them out first - I don't know. But, they weren't wearing life jackets...
Understand all that you can, and how you feel that you may be prepared, and then make your decision. It it's to go, prepare, and be willing to turn around if things go bad, there's no shame in sticking to a plan which includes "turn around if you feel you should"!