This reply might not be useful to OP any more, but might be useful to someone else in the future.
Getting public transit information
In general, if you are curious about public transport in Belgium, you could just use Google Maps. The bus and tram schedules shown are pretty accurate. Trains are excluded though, so if you plan on travelling a larger distance, use our National Railway Company's website or our Flemish Bus and Tram company's website. Both include trains, buses, trams, basically all information regarding public transport. Pretty decent apps are available too if you want to search for information on the road. Search for NMBS (train) or De Lijn (bus, tram, subway in Flanders). They give nearby stops, departure times and itineraries can be calculated, basically any information you'd expect from such an app.
Taking the bus to Blankenberge
After querying it myself, going from Bruges to Blankenberge would take you about 30-40 minutes with bus 33. Bus tickets can be tricky, but you could use SMS tickets (number shown on most stops), buy one on the bus by asking the driver (more expensive and driver might not speak English, but is usually friendly regardless) or buy a 10-session-discount-card at local newsstands.
Sea-cities nearby worth visiting
I'm not from around there, but as far as I know Blankenberge has a beach, Zeebrugge is a harbor, Knokke is the more poche part of the sea with richer people and a Casino, Het Zwin is a nature reserve, Bredene has a nude beach, Ostend is one of the larger sea-cities, etc... I think going to the shore is totally worth it and you could use the Kusttram or "Shore tram" to drive through cities along the shoreline.