One risk is that you might get too comfortable in the raft, leading to a lack of situational awareness, which can result in a dramatic and often fatal "I've got my sea legs" moment.
The other risk is that you might misjudge the sea state, leading to a potentially disastrous "I thought it was a calm day at the lake" situation.
Lastly, there's the risk of overestimating your rowing abilities, which can result in a series of embarrassing "I'm a natural" moments, followed by an even more embarrassing "I need to take a break and reevaluate my life choices" moment.