http://www.boatingmag.com/engines/alter ... c-ski-boat
...with two skiers and three riders on board, I enjoyed the early morning sun through more than 20 exhaust-free ski runs before retiring Correct Craft’s electric Nautique prototype to the dock for charging.
The Ski Nautique E looks like any gas-powered ski boat, sans the engine box. Wraparound seats hide lithium ion batteries, and a Plexiglas window reveals two coffee-can-size electric motors and a single transmission. A receptacle similar to a shore-power plug receives 110- or 220-volt juice to restore the batteries.
At the end of the session, the Ski Nautique E was plugged in for a $3 220-volt charge that would take 4½ hours — just enough time for lunch and for the muscles to recharge before starting the afternoon set.
Full article in the link. No details eg pack size but at 15 cents per kWh, $3 would be 20kWh... `bit more than 2 gallons of gas, so a pretty small "tank".