Possibly a bit big for your suitcase, but if you happen to live near the coast, the Reef Rider Sea Scooter is a piece of Bond-style kit you can afford.
The Reef Rider can carry you along under the waves at up to 2.2mph/3.5kmh at depths up to 3m and with up to 50 minutes use between charges. And for safety, there’s an auto-cut off and a protective grill over the propeller. Just plug it into the mains for charging, with a UK adaptor included in the £99.99. price tag.