There is a major difference as you level. At about 15 swimming, your stamina becomes quite manageable in the water, and around 25 you can swim for a couple minutes at decent speed. I can't count the number of times I was almost to shore and a sea serpent sinks our raft probably a quarter mile from shore and I've made it to land before drowning. (swimming 32 here, and yes, it took awhile lol)