As long as they are under the level cap it's fine for them to arrive just like from any other chapter. The distance from Ashbury to where the Maelstrom is around 1500 miles, as the crow flies, so they might want to figure out what kind of expedition they were on when the shipwrecked, as it wold have been a long-ish one I'd think. There is also the mists, which just recently opened into and out of the Maelstrom. Ultimately it's up to them to figure out how they got into the Empire. If the do shipwreck though they should determine where and how the got to game, as Wyndael is landlocked.
Thanks!