What activities should be avoided when in open areas around and under the vessel swim platform to keep from carbon monoxide?

Never sit on the back deck, “teak surf,” or hang on the swim platform while the engines are running. Never enter areas under swim platforms where exhaust outlets are located—even for a second. One or two breaths in this area could be fatal.

what are the options that have to match them to?

if your boyfriend is cheating on you, my best advice to you is to dump him, he's only going to drag you down. and if you do, don't fret there's plenty better that know how to treat a person right. i mean honestly, the whole point of a romantic relationship is love, and if you love someone you aren't going to cheat on them. i do believe in second chances, but why would he cheat in the first place? i personally feel that if someone cheats, they ruin any chance they wanted/had with you. i wish you the best of luck with this, hang in there.