Do your research. Show up at the easy runs, make friends, offer beers, ask to join a group for a run. Do not overestimate / under-disclose your experience and skills when asking to join a group for an "easy" run. Be honest. Better for them to allow you to join thinking the worst will happen (you swimming and them collecting your gear) and knowing they need to take it slow and show you the lines, etc. That way, if you are better than they expect, they are happy. If you do the opposite, and pretend to be competent but keep swimming and losing your paddle / boat, they will despise you for lying, making them do more work than they hoped for, and won't want you joining their group again next time.