ARK Investment Management took advantage of Coinbase's (COIN) uninspiring second day of trading to add more shares to three ETFs.Cathie Wood's shop has now bought $352M in COIN in two sessions, bringing exposure to more than 1M shares.It bought 341,186 shares on Thursday, adding 33,092 to the ARK Fintech Innovation ETF (ARKF), 25,200 share to the ARK Next Generation Internet ETF (ARKW) and 282,894 shares to its flagship ARK Innovation ETF (ARKK).COIN is up 1.3% premarket.Wood has said she expects volatility in the stock, along with the cryptocurrencies themselves, but sees solid upside.The average price target on the sell side for COIN of about $520 implies a rise of more than 60% from current levels.Crypto trading shifted into high gear this week as Coinbase went public via a direct listing, pushing Bitcoin to a new record high.The "unprecedented demand" for crypto trading led to an outage at Robinhood.Wood also added 42,800 shares