The Ukrainian authorities have announced that any foreign seafarer who sails on a vessel to a port in Crimea cannot visit Ukraine for the following three years, even if then serving on a different vessel and which has not itself called at Crimean ports.
Whilst it is not immediately clear how the Ukrainian authorities will obtain information on individual seafarers who might have sailed to Crimean ports, any seafarer found to have done so also faces a fine or administrative imprisonment for up to 15 days should they try to enter Ukraine
Source: The West of England P&I Club