I have been diving in the Playas del Coco / Playa Ocotal region this week.
There are at least 4 ops here: Rocket Frog, Rich Coast Diving, Deep Blue, Summer Salt. The first two will pick up divers staying in Playas del Coco, Playa Ocotal or Playa Hermosa without charge (not sure about the final two). There are still more ops around Playa Flamingo and Tamarindo.
Conditions: I was told water temps are typically 72-75 F this time of year. We had two days of 80 then temps fell to 76 and 71. Sometimes you can stay above thermoclines, other times top to bottom is cold. Visibility varies wildly from 10 to 80 ft - we have had both on the same day in the same area, with lower vis being far more common.
Wildlife: Not sure what you include in "big creatures". White tips, turtles and various rays (e.g. spotted eagle, cownose, diamond rays) can be seen on local sites. Most people head to the Catalina Islands hoping to see a giant pacific manta but I'm not sure how frequently they are actually seen. In 2 Cat Isl trips (5 dives) I was on the overwhelming majority of divers saw 0 mantas. On 3 dives there were 0 mantas and on the other 2 dives there were 1 or 2 guests who caught a quick glimpse of a distant manta. No mantas were close enough for good photos or video. Any op can take you to any of these sites. There were 2 other boats of divers already in the water by the time we arrived.
Bull sharks are seen at 1 site at the Bat Islands ( Islas Murciélagos ). This time of year only Rocket Frog is running trips to Bats but getting a trip organized will require you to work, especially if you are travelling solo. A minimum of 4 divers are required and even though this is the most expensive trip RF offers, customers are left to find the divers. In our case, Rocket Frog had emails and a deposit weeks in advance from a diver who requested to join all trips to the Bat Isl or Cat Isl but despite multiple emails and a call, they didn't contact this diver when other divers were trying to find more people. If you really want to see bull sharks, make sure you plan enough dive days. One op said they are seen ~80% of the time. We saw some the first trip but 0 the next trip. Mantas can also appear at Bats, but not sure how frequently.
Experienced/advanced divers should know that Rocket Frog will limit your dive time to about 45 minutes. They will write in email that there are no bottom time limits in addition to your gas and NDL limits, but on the boat or at the shop you will be told there is a 45 minute limit or that you must stay with the group (even spouses diving as buddies) which is pulled up around 41 minutes to the safety stop - or potentially earlier when there are newer divers on board. You can try to battle for more dive time, but it is an exhausting and frequently futile process.
The ops usually aren't full and won't commit to dive sites much in advance so you might want to wait until you get here to meet them in person and hear where they are going when you are here.
