Technically, no problems. Normally all lakes have many rivers flow into them and one flows out and that one always goes to the ocean somehow. There are some exceptions around the world where a few lakes do not drain to the ocean - Dead Sea, Salt Lake, Crater Lake. So technically you're okay but these types of lakes are not very common (there's around a dozen, to my knowledge, around the world) and if you start trying to put in every exception to the rule then your maps will quickly devolve into mushy hodge-podge requiring "magic" to explain away all of the inconsistencies. Not that you're going to be that way, just saying to not use geologic anomalies too often. Since this is an island and not some broad flat basin I would expect the lake to have a river drain to the ocean. The wetland placement looks fine to me, you can put those pretty much anywhere where it is low, flat, and gets lot of rain.