The important differrence between the Penguin and the Dolphin is mainly the extra refill hole on the side of the tank. i.e You don't have to take out the atomiser when refilling.

Joyetech themed this series of devices after marine animals, which I think is a bit daft. But they are comfortable to hold in the hand. You can easily cover most of the Dolphin with your palm, in fact , if you also hold a fake cigarette at the same time, it could actually pass as regular smoking. It's a plus if you don't want to attract too much attention.

There are essentially two main parts to this (almost) all plastic construction, the bottom battery housing and the top liquid containter with atomiser. The top clicks in easily and securly on the bottom part with no rattling but as we see later, it breaks off easily with time.

The Dolphin uses the same atomisers as the Penguin belonging to the ATOPACK series, namely the JVIC coil heads which absorb liquid from the top onto a horizontal coil with air flowing sideways. A ceramic 'cradle' is supposed to keep heat focused to help with flavour and vapour production (so they claim), it is more likely made this way to keep heat away from the silica housing that it is plugged into. It is probably the first mod I have with the least metal parts.

The two JVICs included with the kit are 0.25 and 1.2 ohm, with the lower resistance for DTL and and the higher one for MTL. There are others that can be purchased seperately such as  the 0.6ohm (not included).

The kit also comes with a mouthpiece attachment and cartridge attachment, both of which restrict the airflow for MTL. I recommend you not to use these because doing so increases the chance of a dry burn which ruins the wick, which requires a whole jvic replacement. (This happened with the 1.2 ohm).

Operation of the unit is designed for dummies. Five clicks to start and Five clicks to close with a big fire button. This also means the unit will fire briefly when closing.

The short height is very useful for stealth vaping but  with a new Jvic, initial noise and cracks the pod lets out will give it away. This gets quieter with time as the coil is run in. In fairness, it's a lot quieter than most other DTL atomisers.
I would also have preferred the pod to be slightly thinner to be more comfortable when holding. All that being said, the unit did not feel too warm to hold, even when vaping with the 0.25ohm jvic.

The tank sits on top of the atomiser relying on not only with the absorption of liquid into the atomiser but also helped by gravity. The problem with this a top feed design (especially for thick liquids) is that a vacuum builds up above the liquid. And since there is no top air inlet hole (the tank inlet is sealed with a rubber stopper), the vacuum (on top) builds up and inhibits the liquid dropping down. This can result in the atomiser drying up and prone to dry hits.. It can only be resolved by taking off the tank and opening the rubber stopper to let some air in to equalise the pressure. It can be a frequent pain if you have to do this before every vape session.

Another achilles heel is the Tank Lock. It is the flimsy plastic catch that keeps the tank in place when locked in.
To detach the tank, you have to pull it out by force. Over time, this catch will bend and/or break (it's just plastic). Then there is nothing to hold the tank down, except perhaps your fingers. Ironically it's probably best the catch breaks off because you will be constantly taking off the tank anyway to cure the vacuum problem for every session.

The unit is not immune to leaks. Even though you think you've plugged the atomiser in securely, most often, there will be very slight and slow leaks, particularly when carried in the pocket. There was one occasion where I found a small pool of liquid on the top of the battery unit and more alarmingly, at the edge leading down.

This is important to know because any leaks at the bottom of the atomiser will go straight down into the battery housing. The housing cannot be serviced easily because the battery isn't designed to be pulled out from it. The best you can do is to clean up any leakage inside with a cotton bud.

Prevention of leakage into the battery is probably best though. Thankfully, there is some room at the top of the
battery to place a thin layer of tissue to absorb any leaks. The top of the unit will click on without any problems, so this should give you some peace of mind.

Sealing off the top of the battery unit would be an improvement for any future upagrade.

Like most Joyetech products, vapour production is very consistent. Both volume and sustained performance is better than the AIO. It really shows off the JVIC design. This is often under-stressed in most other reviews, the fact that this little device can punch it with big boys. The problem though is it only works for a DTL puff (direct-to-lung). You'll get a lot of vapour, even with a 0.6 ohm coil. But it is only with the 0.25ohm JVIC that you can get bags of vapour because the coil diameter is wider, allowing more air throughput.

An MTL puff on a DTL atomiser (02.5ohm) produces significantly less vapour(like most other DTL atomisers). The quality of the puff may not satisfy pure MTL (mouth-too-lung) users, and at any rate, continual use of MTL puffs will eventually dry burn the atomiser, because the liquid absorption rate is too slow and there is not enough air througput.

In theory, the unit delivers approx 50watts @ 0.25ohm, 22watts@0.6ohm and 11watts@1.2ohm, (assuming no regulation in the circuits and a nominal of 3.6v).  Generally, the lower the resistance, the more vapour you get. I found that there was decent vapour on all the JVICs, infact, for MTL, it is better than most of the tanks that I currently have. The downside is that the vapour tends to be airy, i.e not as thick as I like.

Like most devices, performance deteriorates if you chain vape relentlessly without pause. The Dolphin/Jvic system can sustain high vapour production better than the AIO for chain vaping.

The taste is somewhat lacking, although free from any burning residue (clean). Ironically, I got more taste by DTL than by MTL. Only the DTL would give me a 'buzz' or a 'hit'. I would have to blow through nose to get anything satisfying when MTL. On the plus side, the draw is a lot less harsh than the AIO.

For the 0.25ohm jvic, they could have made the unit a little longer with a bigger battery as vapour production declines when down to 60% (three dots). However, the 2100mah battery should last for at least 2 days on the 0.6ohm assuming you only vape between breaks (as opposed to chain vaping all day).

A very convenient device, not recommend for ex-cigarette users (i.e MTL users) but for intermediate users who know how to DTL (direct-to-lung) who don't want to fuss and can put up with it's faults.