The island aquariunm at Bhimtal inagurated in may 2009,is one of the interesting places for tourist and the local crowd.Situated in the middle of the lake on a small island one has to go by boat to visit the aquarium is government run and the ticket rate is Rs 100/- and Rs 50/- for adults and children respectively. The tickets are sold near the lake before you board the boat .It is open from 11am to 6pm .
A lot of species of foreign fishes like the Piranah,leopard fish, star fish etc have been imported.*
On the side of the Bhimtal lake a famous temple of Lord Shiva is situated known as Bhimeshwar mahadev.This is situated on the side of the water dam.During this travel of the Pandavas they are also supposed to have setup a "Shivlinga" along side the lake, which is presently known as the temple of Bhimeswor Mahadev and is visited by people far and near.
Adjoining the Temple on the same side an area called the "Dart"which consists of several shops,resturants,and boating facilities along with vendors of all kinds ,is a famous tourist area of the region.
You could catch some leeches while walking around during the monsoons... but thats part of the outdoor experience and not much to worry about. They are not poisonous and dont cause any serious issues, except that its not a pretty picture. Blood dosent clot immediately since the leeches inject something that prevents that from happening. Also, its a pretty painless thing, so keep checking for them. Theres scarcely any feeling when they latch onto you.
Carry some salt when you are walking around outdoors (in the rainy season esp) thats the best way to have the leeches peel off...